Ok, until I can find the cause of this crash, I'm posting a workaround.

1. Download the workaround file.
2. Unzip/Extract the zip file "ReinforcementCTD.zip" to your C:\Program Files\Activision\Rome - Total War\Data folder (or wherever you have installed EB).
3. In the folder named "ReinforcementCTD", you'll find a Readme.txt file with instructions for bypassing the CTD.
Quote Originally Posted by README.txt
This folder contains a file for working around
battles which crash to the desktop (CTD) after
the end of the battle.

This workaround will bypass all the trait triggers
as a temporary solution until we can determine exactly
what is causing this CTD.

To apply this workaround,
1. First, save your game immediately before the battle and exit RTW.
2. Next, double-click the file labeled "EB_1_Swap.bat".
This will backup your original traits file and copy in one without triggers.
3. Load up your savegame and play the battle normally.
4. Immediately after the battle, save the game and exit RTW.
5. Now, double-click the file labeled "EB_2_Restore.bat".
This will restore your original traits file.
6. Load up your savegame and continue playing.