Hallo,
I see a similar behaviour with the same MB, but on SHUTDOWN-SUSPEND. I.e. system works, fine, but after shutdown, suspend, hybernate.... system appears off for a few seconds, then "wakes" for couple of seconds before going off again. Lights come up and fans spin up for a "whoof" then it goes off again. It never comes to a proper boot or restart, rather aborts well before anything shows on the screen. It cycles like that forever until I switch off the power supply.
Note when I cut the power supply, it attempts one more time and manages to turn on all the lights on the case for 1s - I assume using caps energy stored in the system - before dying.
Other than that, system behaviour and performance is fine. I have a Sapphire 3870 and a dual core 8200 in there, the PC rocks. So I assume components do not have evident physical bugs or damage.
I have contacted Gigabyte and they said it may be the RAM voltage that needs RAISING from the default. I have OCZ "platinum" RAMs in there and BIOS set to "safe" settings. Tried it. Well, there MUST be a correlation, because with higher RAM Voltage I can get the PC to SUCCEED a full autonomous, unwanted restart after shutdown, but going either way I could not get it to stay OFF!
Note I have made sure that all options for autonomous wake-up (PCI, ring, timer) are off in the BIOS.
Next Gigabyte told me to upgrade the BIOS, which I did to the latest (F3 I believe), but it made absolutely no difference.
So I suspect in the end it IS something with my MB+RAM combination, because I can affect that behaviour thru the RAM voltage, but whether its something actually broken, or a bad setting that eventually can be fixed - no clue.
For the rest I like the MB and system performance is cool. Just the fact it wont stay shut is a nuisance, so I wouldnt want to disassemble and rebuild with a new MB if it can be eventually fixed.
What do you guys think?