I had a look over TE 2 to see if I could spot anything. I can see why you found this so hard to fix - I couldn't even get it to crash consistently.

Anyway, I saw a bunch of minor errors with the sprites. At least one set was borked (Pontic archers I think - looked like maybe it hadn't been converted to DDS). Some riding sprites were not made with the sprite_root flag (so riders looked like they were standing on elephants etc). At least two units were not using the new sprites (east_bedouin). But, alas, I don't think any of these problems would cause CTDs.

I did have a similar problem in XGM a while back with one set of sprites. Somehow the old .SPR file got combined with the new .TGA.DDS files, and that caused problems. My only suggestion at this point is that you start adding sprites back in, a few units at a time, until you run into problems again.