Have you tried the latest BIOS/firmware package for S5520SC? You can get the latest BIOS/firmware package at http://downloadcenter.intel.com/filter_results.aspx?strTypes=all&ProductID=3073&OSFullName=All+Operating+Systems&lang=eng&strOSs=All&submit=Go%21#FRM
And what is the power supply? How many watts is your graphics card?
I don't think this was a BIOS problem as the board would not even POST.
I finally found a number to call and was on the phone with Intel technical support. He had me remove the memory, graphics card, and reset the CMOS battery, but nothing changed, the board would not even start to POST - that is none of the POST LEDs would light up.
In the end I sent the board back to Intel and I am waiting for a replacement.
FYI, my power supply is 1250 watts, the max power consumption on my Radeon 4870 is 283 watts.
Hope the replacement can fix your problem.