MAP 13 CRASH

Map 13 crashes when I get really far into it. It is not at a set action or time though, and is not tied to the number of minions or progress into enemy territory because I have restarted the mission and proceeded differently and still had the problem.

When it is crashing it drops me to my desktop and generates a little windows error box telling me that the game crashed (I did not think to screenshot it or write the error codes down, but I will update this bug report with that information the next time it happens.) When it crashes like this I am unable to load any saved files that were saved recently (save files from early in the mission are still loadable though.) Trying to load a more current save file results in it crashing and giving a "Microsoft Visual C++ Runtime Error: R6025 - pure virtual function call". I have started the mission from early save files that worked and ended up crashing out and I have started the mission fresh from the map/mission selection screen and had it crash out. Each time it makes any save files that are far into the mission become unloadable.

I have tried with massive numbers of minions and I have tried with a much smaller force (heck, one time my minions hated me and kept rebelling, so my army was very small). I have tried attacking the forge in the north east first and I have tried attacking the crypt in the north west first. The furthest I have gotten before crashing out is reaching the first pink crystal I need to destroy to lower the barrier. The earliest it has crashed on me was during an assault on the forge area.