I'm wondering if the forementioned UEFI VGA BIOS could be at play here. Like I said, it's something which manufacturers are having to do now but there are a number of potentially strange, as of yet unknown, compatilibty issues that we might come up against and the warnings from our engineers suggest that early UEFI motherboards could be the most susceptable.
I've sent a message to our HQ engineers to find out if/when we started loading GTX 670's with UEFI. In the meantime, can you download GPU-Z and take a screenshot for me?
on a different subject, if it was a UEFI issue, a Mpower should fix it because this was the first board on the market with fully fledged win 8 certified UEFI BIOS
as for the slightly confusing replies from our engineers, I know the feeling but their English is better than my Mandarin so I can't complain.