blackops wont boot if bios settings are changed

[Tallest]

i have a e8400, blackops, and gskill ddr3 1333 ive had this setup for 2-3 years and it oc'ed with no problems for the first year.
one day it wouldnt boot so i cleared cmos and it was fine, been running default ever since. now im looking to overclock because of issues playing skyrim

nothing i do in the o.c. panel will let me boot, it just keeps hanging without even mentioning "oc failed, press f1 to return to default" which it used to do, now i have to clear cmos every time i change a bios setting.
i have tried:
only setting o.c. to enable, all settings stock and automatic
setting voltage to 1.30v
underclocking to 2.5
setting ram speeds/ratio manually

resetting cmos makes the computer run perfect
i have p07 bios which i installed back when it was new, any ideas?

[PiLsY]

Try disconnecting all power and removing the cmos battery. Short the cmos battery terminals with a screw or something. Itll give it a really good clear that way.