I have OC'ed my Q6600 to 3GHz on a ASUS striker extreme motherboard, but i am facing some little problems.
Every now and then the computer resets itself and just before that a blue, DOS-like screen for about a second with some text on it but i can't read it because it goes to fast.
Apart from that i am also getting some errors when trying to unpack some winrar archives.
that sounds like your core voltage, it needs upping, i think. what is your bios set at for all voltages and others?
i have set all voltages to auto except the cpu vtt voltage. that one i have set to 1.55 v because otherwise the pc already crashed when loading up the desktop. With the core voltage on auto, the mobo is setting it to 1.31v and i have already tried higher voltages to about 1.37v but this is the most stable one.