Sounds Like a RAM problem to me...
Sounds to like a ram problem to me...
What brand are you using?
I swear by Kingston, but many pro builders like myself also like:
Corsair, Crucial (Not my favorite), Mushkin, etc.
The RAM market is very similar to the power supply situation.
YOU GET WHAT YOU PAY FOR!
Dont expect clear sailing on Kbyte RAM, particularly on a high quality mobo.
A good example is when a customer requested an ASUS board, but wanted to use this crappy Kbyte PC2700 DDR he bought from Office Max on sale. The board was great but untill we got a good stick of Kingston in there, it crashed all the time and had the same symptoms as yours. Most usually it crashed during video games.
Sounds like your memory is not refreshing properly and is loosing critical system information like the USB file you refered to. When the system tries to get at that file and can't find it at the address it sent it to, it freaks out and stops the system to protect itself.
Thats Microsoft for you. Rather than write scripts to recover from this type of problem, they'd rather have the system halt and you loose all of your work!