got an asus p5n-d? help please xD

Well ive had my rig since the beginning of feb but i cant seem to get my cpu(e8400) past 3.6ghz, any1 else had this issue with going over 1600(400fsb) on this board? and any1 know what the stock volts for the NB etc etc are because asus keep ignoring my question and say something else :P.
Sometimes it will boot @ 3.8ghz but will not load windows as it says missing file/corrupt *name* but goes away when its back to 3.6ghz, could it be the cpu is a weak one? any idea on volts i should have for it because at 3.6ghz its only @ 1.18 but in the bios i set it to 1.225(stock rated).

Thanks

edit: also, what voltages are on safe for running a rig like mine(in my system)? because the Xclio although has given me no issues but out of curiousity is 11.9V at load bad? this is reported from the motherboard(asus probe) so could be off, the 3.3v is at 3.23 and 5v just stays the same, they all safe?. How would i go about getting the correct reading i.e using a multimeter.