I am having a simular situation. All I did was straighten up the inside of my computer case, putting wires in more hidden situation and organizing the connections for a cleaner look and now my POST has gotten extremely slow. It will start up fast, showing the correct amount of RAM and when it starts showing the ram timing the type slows down to where you can see it type out everything from that point on. Then it seems to lock up for 15 minutes trying to detect IDEs. I've attempted to go into bios but can't seem to move around with my current keyboard, so going to hook up a different one later today to attempt that again, reset the bios, nothing, attempted to flash the bios it locked up.
Board : Nvidia 790i Ultra SLI
RAM: 8GB (4 X 2GB) OCZ Technology DDR3 1333 (PC10666)
Video Card: Nvidia 9800 GX2
Processor: Intel Core 2 Duo E8500 3.16Ghz.