Anyone give me advice please?

I've two of everthing so have been able to do some intial tests, everything is new and just been fired up:-

I have a problem with 1 of the Blackop boards, with the QX6770 in it at stock settings running Everest, 2 of the cores cause prime 95 to fail after arroun 30 seconds or so, Everest fails after 30 seconds and some times runs a litttle longer but then the same cores fail. Temprature is fine. I'm sure this is mobo problem coz the same bits work fine in the other Blackops mobo.

Am I missing some settings to get the mobo stable before oclocking or do you recon this is a duff mobo?
Thanks