I notice that you've got the same board as me, well the RAID version. Question... have you found NB voltages a problem area on this board?
I had it OC'd quite high 3.6gig on an E6600 which was fine for awhile but then during the summer (well the few warmer days we had) I started getting that error and random crashes in games... ran memtest and it came up with loads of random errors (which didn't seem like a RAM problem to me) - tried the RAM in my other PC and it checked out fine - so I put a fan on the NB and dropped the volts on it back -0.1 and its been fine ever since.