Yeah join the club. I switched to bigadv and had the system lock up twice, no BSOD that I could see. Luckly I didn't lose the progress.
However I switched back to standard big last night at 04:00, went to bed and then woke up this morning to find it had BSOD in the night. IRQL_GT_ZERO_AT_SYSTEM_SERVICE what ever that means.
So maybe the overclock isn't stable or the PSU is on the way out or something. I'm back to stock for the timing being, so far so good. Not quite sure what the issue is, was running nearly 2 weeks without a problem previously.