You can try resoldering the CPU onto the motherboard, maybe one of the pins got loose. On a more serious note, there's obviously not enough information here to do anything. 
__________________
ASUS P5K Premium WiFi-AP, Q6600@3.7 / ASUS P5ND, E6400@3.8
4GB OCz Platinum XTC 8500 / 4GB CorsairXMS2 6400
5x500GB Seagate 7200.10 / 2x500 Seagate 7200.10
OCz 8800GTX 768MB @ 630/800 / 2x Galaxy 8800GT SLI
|