Mine is now sorted with the EK block......conclusion....the card is cold buged at temps below 28/30C. I have to sometimes disengage all the fans on my Swiftech MCR420 and just leave the pump going so that the card heats up and stays above 30C. Upon first boot up I usually have to run GPU-Z to check temps and fire up furmark straight away to get the cores above 30C, after that everything is okay.

CHanging 2D clocks via the xml file or dissabeling ULPS doesn't do anything for me....it's all about the temps.