|I once saw this exact problem on an amd based system (I think it was an athlon 64 3300+ or something similar). The only thing that got it to boot was a new processor; the original processor was supported by the board according to the documentation, I didn't try it in any other pc because it wasn't mine, went back with the people I fixed the pc (ebay special) for.|
Many things can cause these symptoms as mentioned above, I have seen it caused by corrupted cmos, but it is unlikely. None the less it shouldn't hurt to try clearing the cmos again with minimal hardware connected (cpu ram and graphics) by removing the battery and if available using the jumper. Try to boot with the minimal hardware connected.
It depends on how in depth you want to trouble shoot it, I would slowly strip it down until all that was left was a know good and tested PSU, speaker and power switch connected to the motherboard, testing periodically along the way, but it may not be worth it.......
If this is a result of a bad bios flash, you could try the recovery techniques. Or uniflash in a "hot swap" on another mother board (and if it really a bad bios chip a compatible one) as a last resort.