You willl (eventually) find that 5.1 OC is not going to be stable and upon lowering it to, say, 4.5 or 4.2 that it will then be stable yet give you the performance you need. When you get PC stable let your 'PC Guy' know what you did. He will no doubt say 'Oh, ok' (and smile because he suspected the 5.1 OC was NEVER going to be stable but wanted you to THINK he was a 'great' tech - which is not always the case!).
Chuck B
Napamule