GTX not overclocking after cpu overclock

[Born_2_Kill_83]

Before overclocking my CPU @ 3.0 the highest clock I could get my Asus 8800GTX to was 659/1040, now I'm lucky if I keep it stable over 600/1000. 3D mark 06 will crash out with a .dll error of some sort and the screen keeps going off and on. Where am I going wrong and can any-body give me some tips.
Thanks

 

[helmutcheese]

If you have OC'd the FSB in your bios you may have forgot to lock the PCI-E bus so it is now overclocked to much, it should ideally be set to 100mhz but many find 101mhz or 110mhz is more stable.