I have the same problem with Asus ENGTX560 TI with P8H67-V and P6T Deluxe series. The same VGA card works fine on Supermicro X7DAL. I also updated the GTX560 Bios with the more recent version available. Same problem.
I've now tried switching PSUs and starting the system up outside the case ( Removed the MB and all components) , still no luck, it would seem that some MBs just cant communicate with some video cards for no apparent reason , but since there was no way of checking if it would work prior to my purchase im now stuck with a card I cant use, will probably have to upgrade MB + CPU or sell it :/