Unstable reboot (990FX Killer/3.1)

Hi,

Years ago I bought a Fatal1ty 990FX Killer/3.1 motherboard. I am now facing two strange issues and when I have to find the culprit between a motherboard with a year warranty and a 750W PSU with 7... I first have to see if it is a issue with the motherboard.

Link to Asrock Motherboard page:
http://asrock.com/MB/AMD/Fatal1ty%20990FX%20Killer3.1/index.asp

The main issue is that often my PC will not boot if I perform a restart on Windows or try to save or even not save the settings in BIOS, which also triggers a reboot.

I then have to force shutdown and turn it on multiple times for it to either boot or trigger failsafe, which sometimes allows it to boot. Most often I need to wait with the power cord unplugged before attempting to boot again.

So far I think it is a PCI-E related issue as the PC would often boot when there is no graphics card attached. I've faced this issue with a low-end and an old extra-powered mid-tier graphics card. Will try to attempt getting a 4-pin speaker in order to find out at least something that does not allow it to boot.