Third Age Total War Error Thread

My son wants to play this game, so I've helped him install the Medieval 2 version of Total War (purchased from Amazon & downloaded) and installed the First Age Mod with 2 patches (3.1 and 3.2). When we started the game, the video at the beginning runs, and it allows him to select which game he wants to play, so he is selecting single player, custom game, and when he gets to play after selecting his options, he gets the following error: "Medieval 2: Total War encountered and unspecified error and will now exit."

Regular Total War Medieval 2 runs just fine and he does not complain about error messages on that, so I figure it has something to do with the mod, but I don't know what or how to resolve the issue.

My initial thought was that perhaps it had something with some sort of custom culture- huge city, etc. that the game says is required for certain venues, however even playing on one that did not indicate that requirement it still giving me the same error and closing out. My son thought that perhaps the quantity of troops was the causative factor, however even utilizing one small band of troops (infantry- 158) per team still caused the same error.

So this is what we've tried so far, and I am out of ideas at the moment and do not see any topics on this issue, but am hoping someone has an idea? We've tried this on 2 separate computers- mine which is running Win 7 and my hubbys gaming computer also running Windows 7. Both ran into the same error message.

Please bear with me- I am not a gamer or a developer, just trying to help my lotr obsessed son get his fav. game to work. Thanks for any help offered!