I was OCing and benching a lot around the new year but have since been running at 4.5... (2500K)
What voltage you been running?
Obv if doing at stock its not the oc thats causing it.
Possible to corrupt os by pushing the oc too far but been years since its happened to me...back in socket A days i think and was caused by the oc on the ram that went with it rather than just cpu oc as we can do now.
How long since you did a clean install?
Checked for malware etc?
Good thing to do after clean install and getting all setup as you like is to make a recovery image on an external or mem pen...then you can just boot from cd and tell it to repair using that image..back up and running in 15 mins or so.
Life saver if you get a nasty virus (fixing someone else's computer)
Need a disk still though for that.
If memtest shows up then do the usual one stick in different slots test to find out which it is (or even if its a slot at fault)
Raising the voltage for ram can (sometimes) overcome error but if it wont run memtest at stock then RMA if under warranty.
(ps a sig is handy so we know what you have

)
Hope you get it sorted
