Unspecified Error. (Steam user)

[ArcticSwarm]

I have Medieval II Total War and Medieval II Total War - Kingdoms, which were bought using Steam. I previously had Medieval II Total War installed from CD, but removed it and then installed the game through Steam. I installed part one and two from here, http://www.moddb.com/mods/third-age-total-war. Then I patched the game, I tried using Squid's launcher ap as well as a 64x registry thing (can't remember exactly what xD) I found on this forum. Niether of those seemed to work with my issue.

My issue is that when I go on custom battle and select a map and then a level from the drop down, I get the pop up which basically says it's closed from an unspecified error. I've seen about posting the system log.txt file but can't seem to find it? I haven't tried any other game modes yet as I wanted to give custom battles a go first. Any help would be lovely, I really want to start playing. xD

If my system specs is required, let me know. But I'm 100% sure I can run it.

Edit ; Oh and if I try to run it using the Total War Third Age icon, I just get Medieval II has suffered a fatal error and will now exit.