Some have the 570 some have the 590 - hence why some may be having problems and others not. Why a SB should affect the FSB I have no idea but I can't see any other reason as on dualcore I could exceed 500fsb easily and it was stable (500x8) - no such luck with this quad tho - its either stable or wont boot, no inbetween. Usually prime starts to get flaky once you are hitting the cpu limit but for it to go from stable to no boot with a 1mhz increase is bizarre.