I have a dual-core AMD with a GeForce 9500 card, and have been experiencing random lockups.
I haven't found a way to reproduce them, but the only thing that works is to power off - the machine is completely dead. I've talked to others who have the same problem - it seems to be related to the combination of a dual-core AMD Motherboard and an nVidia video card. I had a similar problem with the on-board graphics (nVidia 7025) except that the screen would corrupt.
I would really like to determine the cause of this. Is there any way to turn on additional logging that might help determine the cause of this?
Update:
I installed Fedora 11, and it's doing the same thing: random freezes. I guess the next step will be to try Win7 to see if it has the same issues.