what oc software are you using or are you ocing thru bios?. if in bios reset cmos or go into bios and load default and exit' if amd then load default in advance settings or in preference. hope this helps some.
Open BIOS and select "Set all to defaults". Process will be well described in your MoBo manual which if you don't have can be downloaded off manufacturer's web site.
Reboot your PC press delete and in some PC its F2 go to Exit menu choose Load optimized Defaults and then save and exit.