I didn't make it!
OK, Im running XP and as we all know the game has a lot of issues with Bill's latest creation. I have tried everything, uninstall/reinstall low quality sound/graphics, new drivers, new graphics card/sound card nothing would stop this game from crashing.
But now I have a "kinda" solution, I have noticed that the lockups tend to occur with the auto save files "Checkpoints". Looking into this further I find that these files are not being written correctly, some are only a couple of bytes long while others (that work) are at least 900K. Even if you load a different/manual save file these corrupt auto saves still affect the game. The only thing to do is delete the most recent "checkpoint" auto save files you can find, don't worry about ones at the beginning of the game, just the last couple should do. Then start from your last manual save and play the level all the way through. its best to try and do a manual save before the last check point of the level. That way you can delete the "checkpoints" and not loose too much ground .
Hope all this makes sense.
;) did you try reinstalling the game and deleting all your game settings and pk3 files?