Ah, what a shame. Would you mind confirming that Steam is the problem by way of looking at my log?

18:15:06.383 [system.rpt] [always] CPU: SSE2
18:15:06.383 [system.rpt] [always] ==== system log start, build date: Sep 5 2014 version development ===
18:15:06.383 [system.io] [always] mounted pack packs/data_0.pack
18:15:06.383 [system.io] [always] mounted pack packs/data_1.pack
18:15:06.399 [system.io] [always] mounted pack packs/data_2.pack
18:15:06.399 [system.io] [always] mounted pack packs/data_3.pack
18:15:06.399 [system.io] [always] mounted pack packs/data_4.pack
18:15:06.399 [system.io] [always] mounted pack packs/localized.pack
18:15:08.588 [data.xml.tag] [error] File:[mods/TwoThrones_1.0/data/descr_movies.xml]Error: empty tag.(4:26)
18:15:08.593 [data.xml.tag] [error] File:[mods/TwoThrones_1.0/data/descr_movies_tracks.xml]Error: empty tag.(6:20)
18:15:09.599 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1087, column 110
unit(cog) does not match up to the ownership for faction(moors)
18:15:09.600 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1105, column 110
unit(cog) does not match up to the ownership for faction(moors)
18:15:09.600 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1107, column 104
unit(holk) does not match up to the ownership for faction(moors)
18:15:09.601 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1125, column 110
unit(cog) does not match up to the ownership for faction(moors)
18:15:09.601 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1127, column 104
unit(holk) does not match up to the ownership for faction(moors)
18:15:09.602 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1147, column 110
unit(cog) does not match up to the ownership for faction(moors)
18:15:09.602 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1149, column 105
unit(holk) does not match up to the ownership for faction(moors)
18:15:09.603 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1178, column 110
unit(cog) does not match up to the ownership for faction(moors)
18:15:09.604 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1196, column 110
unit(cog) does not match up to the ownership for faction(moors)
18:15:09.604 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1198, column 104
unit(holk) does not match up to the ownership for faction(moors)
18:15:09.605 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1216, column 110
unit(cog) does not match up to the ownership for faction(moors)
18:15:09.605 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1218, column 104
unit(holk) does not match up to the ownership for faction(moors)
18:15:09.606 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1238, column 110
unit(cog) does not match up to the ownership for faction(moors)
18:15:09.606 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_buildings.txt, at line 1240, column 105
unit(holk) does not match up to the ownership for faction(moors)
18:15:09.815 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_guilds.txt, at line 166, column 44
Building level name mustering_hall not found as a level in building database
18:15:09.816 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_guilds.txt, at line 238, column 44
Building level name militia_drill_square not found as a level in building database
18:15:09.816 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_guilds.txt, at line 247, column 44
Building level name militia_barracks not found as a level in building database
18:15:09.816 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_guilds.txt, at line 256, column 44
Building level name army_barracks not found as a level in building database
18:15:09.816 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_guilds.txt, at line 265, column 44
Building level name royal_armoury not found as a level in building database
18:15:09.817 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_guilds.txt, at line 1227, column 44
Building level name stables not found as a level in building database
18:15:09.817 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_guilds.txt, at line 1245, column 44
Building level name earls_stables not found as a level in building database
18:15:09.818 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_guilds.txt, at line 1611, column 44
Building level name gunsmith not found as a level in building database
18:15:09.818 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_guilds.txt, at line 1620, column 44
Building level name cannon_maker not found as a level in building database
18:15:09.818 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_guilds.txt, at line 1629, column 44
Building level name cannon_foundry not found as a level in building database
18:15:09.818 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_guilds.txt, at line 1638, column 44
Building level name royal_arsenal not found as a level in building database
18:15:10.198 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_ancillaries.txt, at line 2359, column 43
Building level name stables not found as a level in building database
18:15:10.198 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_ancillaries.txt, at line 2382, column 43
Building level name gunsmith not found as a level in building database
18:15:10.198 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_ancillaries.txt, at line 2390, column 43
Building level name stables not found as a level in building database
18:15:10.198 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_ancillaries.txt, at line 2438, column 43
Building level name militia_drill_square not found as a level in building database
18:15:10.199 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_ancillaries.txt, at line 3222, column 43
Building level name catapult_range not found as a level in building database
18:15:10.200 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_ancillaries.txt, at line 3410, column 43
Building level name army_barracks not found as a level in building database
18:15:10.200 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_ancillaries.txt, at line 3472, column 43
Building level name catapult_range not found as a level in building database
18:15:10.200 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_ancillaries.txt, at line 3490, column 45
Building level name siege_works not found as a level in building database
18:15:10.200 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_ancillaries.txt, at line 3620, column 43
Building level name earls_stables not found as a level in building database
18:15:10.202 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_ancillaries.txt, at line 4945, column 45
Building level name gunsmith not found as a level in building database
18:15:10.268 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 14329, column 42
Building level name stables not found as a level in building database
18:15:10.268 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 14330, column 42
Building level name militia_barracks not found as a level in building database
18:15:10.268 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 14343, column 42
Building level name stables not found as a level in building database
18:15:10.268 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 14344, column 42
Building level name militia_barracks not found as a level in building database
18:15:10.268 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 14527, column 29
Plug-in/Building level name cannon_towers not found in building database
18:15:10.268 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 14545, column 29
Plug-in/Building level name c_cannon_towers not found in building database
18:15:10.269 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 14581, column 29
Plug-in/Building level name militia_drill_square not found in building database
18:15:10.269 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 14590, column 29
Plug-in/Building level name militia_barracks not found in building database
18:15:10.269 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 14599, column 29
Plug-in/Building level name army_barracks not found in building database
18:15:10.269 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 14608, column 29
Plug-in/Building level name royal_armoury not found in building database
18:15:10.269 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 14617, column 29
Plug-in/Building level name mustering_hall not found in building database
18:15:10.270 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 15040, column 29
Plug-in/Building level name ballista_range not found in building database
18:15:10.270 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 15049, column 29
Plug-in/Building level name catapult_range not found in building database
18:15:10.270 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 15058, column 29
Plug-in/Building level name siege_works not found in building database
18:15:10.270 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 15067, column 29
Plug-in/Building level name c_ballista_range not found in building database
18:15:10.270 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 15094, column 29
Plug-in/Building level name gunsmith not found in building database
18:15:10.270 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 15103, column 29
Plug-in/Building level name cannon_maker not found in building database
18:15:10.270 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 15112, column 29
Plug-in/Building level name cannon_foundry not found in building database
18:15:10.270 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 15121, column 29
Plug-in/Building level name royal_arsenal not found in building database
18:15:10.271 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 15499, column 29
Plug-in/Building level name stables not found in building database
18:15:10.271 [game.script] [error] Condition parsing error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 15517, column 29
Plug-in/Building level name earls_stables not found in building database
18:15:10.272 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 15860, column 42
Building level name stables not found as a level in building database
18:15:10.272 [script.err] [error] Script Error in mods/TwoThrones_1.0/data/export_descr_advice.txt, at line 15861, column 42
Building level name mustering_hall not found as a level in building database
18:15:11.061 [system.rpt] [error] Medieval 2: Total War encountered an unspecified error and will now exit.

I actually have the disk version but it didn't work last time I tried so I just moved to Steam. Looks like it might be time to bust it back out and make a serious attempt to fix whatever is wrong with it. Thanks for the response anyway!