Id do a search, im sure someone else had this problem with a Gigabyte board, when they took the 12v job out theres powered up as well, with it in was a no go, i'll have a look around myself and if i can find it again ill link to it.
Sounds a bit like
this , when he didn't have the 4 pin in it booted as well, but hes RMA'd the board, id try as suggested in there, a cheapo stick of Ram to see if you do have the memory voltage prob, then if you get it up and running with the cheapo stick you can up the voltage in the BIOS so you can get your Geil up and running.
Does sound like a faulty board though, as the Geil's running perfect for me, booted up first time when i put it together, so i cant see it being the voltage problem, so id be pointing to the board, but you never know so a cheapo stick is worth a try, may as well rule it out before you RMA it, just in case they find it fine and send it back to you.