And I would still go for a limited memtest. Because these problems do resemble RAM fault. It is a little more complicated though, since you will need to prepare a separate bootable drive or CD/DVD. So we can skip it for now and go back to it later if other fixes won't work.
Here are instructions on how to perform a memtest:
http://answers.microsoft.com/en-us/w...f-ecc7b7ff6461