What could cause that effect is the PCI bus being out of synch. If it is unlinked to your FSB (i.e. your FSB speed does not affect your PCI bus speed) then the data signals are likely not synchronous.
If your FSB and PCI buses are linked, then the problem should go away.
Check in the BIOS for an appropriate setting.
I couldn't find an option to do so, possibly because I'm on a laptop. However, I did take a screenshot of CPU-Z when overclocking and the FSB speed does seem to affect the bus speed; unless this occurs even though they are unlinked.
Are there any other solutions?