Ah, I think I know what's going on.
If you installed the AC mod over gjoerulv's mod, you may have overwritten the battle model for the "robot" enemy that gjoerulv made. It appears in that part of the reactor, and if you don't have its model the game will crash.
I recommend that you reinstall gjoerulv's mod on a clean copy of the game, make a backup of the patched battle.lgp and put a clean one in the main game directory, patch the clean one with the AC mod, take the player character models out of the AC mod patched battle.lgp file with lgp tools, use lgp tools to put them in the battle.lgp file patched with gjoerulv's mod (so you don't overwrite any of gjoerulv's enemy models), and then put *that* battle.lgp file in the game directory. I haven't tried this myself, but if do that, you should be able to make it work.