This is quite spooky,I have just swapped my Asus P67 mobo for a Gigabyte P67 mobo, for no other reason I won it so I thought I would see if it was any better than the Asus. I had the exact same problem as you and it took a bios update to sort it. From the original F1 to the latest F3. The problem has gone.
What is ransomware and how do I protect my PC from Petya?