I'm on a q9450@2.66 4x1GB corsair ddr2@1066 8800gts 512 running windows 7 64bit.

Two days ago I started getting bluescreens, now they happen once every 5 6 hours, the bsods say either pfn list corrupt or memory management, about 1 minute before each blue screen my internet connection fails (I'm on wireless), programs start crashing and the windows aero interface turns off.

I ran memtest86+ after my first bsod with no errors, I was impatient and only let it do two passes. I then scanned for viruses, cleaned my fans, adjusted my ram voltages which for some reason had reset to auto undervolting my ram.

Last night before going to bed I got another bsod and decided to let memtest run all night, right after the bsod I booted memtest and it started reporting a lot of errors, in the 30 seconds it ran I got around 500 errors, I rebooted, my motherboard decided to load it's bios defaults again, I changed my ram voltages and started memtest again. This time it ran all night doing 9 passes and got no errors.

Any idea what could be causing this? How can memtest report errors only sometimes?

Random errors are tricky and annoying. I believe you've tried googling for the exact error adresses in the bsod so I'm not going to suggest that. ;P

Judgeing by your symptoms, the problem lies either in the motherboard or the memory sticks, or both. Could also be abnormal voltage so just to be on the safe side what Power Suply do you use?
Have you tried running with each of the mem stick alone and swapping them in different memory slots?
At which memtest Test do the errors pop up?
Did you still get errors after removing the personal bios settings? If so you could try a bios update.

I'd suggest you try and test it a bit longer. If the problems persist in the same manner (they go on and off) try to test the memory sticks on a different system.

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Comfortably Numb

If you have other RAMs at hand... try an exchange. If not try what Sebasssss said... different RAM slot combinations. Could easily be a faulty RAM.

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SaintK: I'm completely lost

Try the black slots. Or the other ones if they're some different color.

As for ram, check the sticks for exact settings and enter everything on it into the bios - don't change a thing.


Oh yeah, and did you check if the fan even works or just cleaned it

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SaintK: I'm completely lost

Yeah, PS overheating and messing up the voltages it puts out could also cause random system faults.

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Comfortably Numb

Apparently formats can fix anything.

Temporarily.

Move your PC to another location.
Its propable that a star-constellation moved into position which focuses a high amount of cosmic rays onto your RAM, flipping your bits and causing random BSOD!