P.S. I blue-screened for the first time today...three days after I was Prime95 stable for 12 hours.
As mentioned by photon boy put all your settings to stock and if it works properly you know it's an unstable overclock. Also Prime 95 stable doesn't mean your system is always, no matter what, totally stable. On my previous overclock settings my PC did 13 hours of prime 95 no problem but crashed playing COD:World at War after 15 minutes.