I'm having a similar problem (I think). I installed a Cougar Video Edition Card and it often hangs whenever it has to do something serious. Ctrl-Alt-Delete doesn't reset anything and I have to turn it off at the point.
I have an onboard video card in my new PB. I've heard you have to actually disable it physically, but when I rang PB tech support the guy said "no such need". He just told me to change the BIOS to always start on the card I installed.
I have scoured the Web and can't find anything to help me. I love my games so I'm getting edgy. Please help.