I sneak up to the Quarry, and attack a Deathclaw, it turns hostile, CTD.
I walk over, attack, CTD.
I attack a Legion guy, CTD.
I use different weapons, CTD.

Unless I get a one shot kill it just shuts down

Oh, and thanks for letting me search the forum to update the last topic I started about this problem only to find it's been deleted.

I built a PC to play this game - i7-920, HD5770, 6GB RAM, Hybrid HDD and it looks no better than on my old E2200 with AGP HD3850

Fallout 2 runs great though

**EDIT**

The problem was Cass - as soon as she turned hostile towards an enemy - the game crashed!
(I knew I should have taken her shopping... for plasma guns....