Hi guys, I have a bit of an odd one here. My machine will not shut down at all, that is not unless I put it to sleep first, wake it up and then tell it to shut down (wtf?!). This started last summer almost a year after I put the rig together, it didn't always used to do it but now its just driving me mad as I cannot find out what the hell is causing it!

Here are my specs...

i7 920 D0
DFI X58 T3eH8
6GB Corsair XMS 1600MHz 7-7-7-20
Radeon HD6950
Corsair HX650W Modular PSU
1x WD Velociraptor 300GB
2x 1TB Spinpoint F3
Windows 7 Home Premium 64-bit

Now for what I've tried to no avail...

I've reset the BIOS to fail safe (back to stock from an overclock to 3.8)
Re-flashed latest BIOS
Flashed older BIOS
Reinstalled Windows 7
Tried shutting down from Linux live disc
Changing all sorts of BIOS settings relating to power management
Unplugging devices and peripherals in case one was causing it to stay awake
Tried the supposed enable power management for VIA Firewire controller fix

Things I've replaced since after it started...

Upgraded 4980 to 6950
Upgraded PSU from Enermax 580W to Corsair 650W

I cannot for the life of me work out what is causing this. The BIOS status code display on my DFI board states FF at all times once it has got in to Windows (which is normal) but doesn't change from this once the shutdown command is issued. If I tell the machine to shut down it will remain in a powered on state forever until I press and hold the power button, if I simply press the power button the power LED on the case will flash about 10 times and then the machine will power off, only to come back on a few seconds later, sometimes after this my machine will report only 4GB of RAM is usable in the machine (Windows will see 6GB but say only 4GB of that can be used).

What's odd though is if I suspend the machine and then wake it up it will shut down fine from there.

Here are two Youtube vids I made so you can see the issue...

Shutdown - http://www.youtube.com/watch?v=82INmfTudWM
Standby and shutdown - http://www.youtube.com/watch?v=QLdkZf87bmw

I truly have no idea what to do with this and its driving me mad.