Have same issue. Your not alone. New GTX760 (GV-N760OC-2GD) on the "Military Class" 990FXA-GD65 mobo. Video card is an upgrade to a 18 month old build (mobo was new in July of 2012).
AMD FX-8100 series processor
750W corsair power supply
Get the post "beep", no display. Shows "B2" in the lower right corner.
Deleted the video drivers, No help.
Tried both video card slots, no help.
Put the GTX760 into another machine with a different mobo and it workes...
Looked at the BIOS of the 990FXA, don't see where any change could be made to video.