Make sure your pci-e frequency is set to 100 in bios. It can be set to auto sometimes and if your o/c other things, it might be higher than 100. Google o/c pci-e frequency and you will see that it kills video cards and hard drives. I've not witnessed this first hand, I believe.
hmm where would i find this "frequency" ... i dont think i have any BIOS options for PCI-e but i will have to take a look and get back to this