Dude had exact same problem. I add a brand new pc to my network would run fine except as soon as you tried transfering files of any significant size the pc would lock solid, I also noticed it was corrupting data as well. this was a Duron 750 O/C to 1Ghz on an abit kt7a I did all the above. I even disabled the l1 cache, with this diabled ran with no problems just took a week to do anything but never crashed turned out to be faulty mobo. When I took it back to the retailer I met someone with the exact same problem same mobo and chip. Got new board and just to be safe they gave me a new chip no probs ever since.

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You can run, but you will only die tired!