Just in case others have this issue - I upgraded to the GTX 770 OC in my i7 3820 system and couldn't get it to boot past the bios splash screen and none of the keys to get to bios worked. The solution was to reinstall prior card to get to bios and change the PCI ROM from EFI to Legacy ROM. After this the system booted no problems and all sweet.
If anyone knows what I miss out on by using the legacy ROM it would be appreciated, also if there is a fix in development to allow the GB card to be recognised by the GB motherboard without using the legacy ROM. I am using the F2 bios (didn't want to flash with a beta version just in case).
Thanks from sunny Oz (....and lets not talk about the cricket....)
Thanks David.