I'm experiencing a wierd problem with this computer. About 5 minutes after booting the machine freezes into a blue blank screen (not BSOD). The screen is completely blank, not even a cursor is visible. After a reboot however the computer works just fine and no more blue screen occurs. The next day the same thing happens, but only on the first boot.
I've testet the RAM with both memtest86+ and the native tester in Windows. Neither found any errors.
So, any suggestions?