to make sure run, run prime 95 at stock speed and see if it crashes. If it still does, then something else is wrong. If it doesn't, then your system was unstable with that oc.
A great stress test other than prime 95 is intel burn test. In my experience it has worked better and has been more accurate for me. Sometimes it takes prime 2 days to detect instability that intel burn test can detect within a couple of hours.