motherboard post says no vga but vga is working advise?

rig: asus p6t deluxe v2
OCZ ddr3 1600mhz 6gb ram
core i7 920 @ 3.8
Sapphire 1gb HD4870 w/ t-rad 2 cooler
Corsair 750tx psu
HAF 932 case

I built this computer and it ran fine for about 2 weeks then all of the sudden it wouldn't not boot at all. it tuns on for a second then beeps an error code. the monitors dont even turn on. It beeps 4 times, so i looked it up and the Asus manual says that means no VGA detected. so i opened the case and checked the VGA card. It is properly seated and the power cables are plugged in. So i turned on the computer to check the error code on the graphics card and 3 red led's turn on for half a sec then turn off. i read that if there was an error they would stay on, which they didn't. So that means the vga is fine (hopefully). i don't have another vga card to test or another computer to put the current VGA card in to test. I have also tried resetting the cmos and that did nothing as well . Just still the same beeps. i have no idea if its the motherboard or the graphics card. i really dont want to have to RMA either of them so im hoping for a fix... Any advise would be greatly appreicated!
Thanks in advance

I would remove the hold down screw for the 4870 card and try again. The card may be slightly crooked and not making good contact with the board. I've seen this problem even with high end cases where the board doesn't line up with the openings for the cards. Carefully reseat the video connections to the card and the LCD. Then reseat the power supply 24 pin and 8 pin connectors to the board. Then try booting up again.