Thanks to all for the different information on this BSD problem. I fixed mine but it was so different from anything on here I thought I should share it.
Basic machine specs:
Planar - ASUS AN8-SLI Deluxe (with a replaced fan for the video chip - grumble, grumble)
CPU - AMD Athlon 64 FX-55
Memory - 2GB DDR400 RAM
Vidoe - 2 x nVidia 6800 Ultras
PSU - Thermaltake PurePower 680w PSU
and various other stuff all relatively new (less than 2 years).
Another background note: the Machince Check BSD only occurred when trying to rip a CD to my HD. Everything else seemed to work fine (although I didn't try games and such).
At first I thought this was due to a recent monitor change (out was the Viewsonic VX-900; in was Apple's 23" HD Cinema) as I was having some other anomalies surrounding it. I read through all of the posts and then realized that couldn't be it and began to think it was a PSU or heating problem. That was quickly dispensed with since the room in this house (I live in North Yorkshire) is always nice and cool and the system's PSU is a beast. I then thought it might have been the UPS, but that proved to be a dead end too.
So then I started working backwards to my own "last known good" and then in an ephinanic moment it dawned on me. All of this started after I popped in a Sony CD that contained the XCP software. Norton caught the spyware but something else must have been causing this problem. I did some research and went to Sony's site, downloaded and used their removal tool, rebooted, and voila - NO MORE PROBLEM.
I stopped trying to figure out why and decided just to be happy that it's fixed. For the life of me I have no clue why this worked...
Thanks again to everyone for the good information!
Regards,
Scott