Hey I got a problem with this board and cannot get it sorted. Every time I try to shutdown, it turns off then powers back on by itself a few seconds later so I have to turn it off at the PSU switch

Is this a common problem with these boards and does anyone know what might be causing it? Any help would be great Im about to go nuts trying to solve it.

All settings are at stock, ram settings are configured manually. These are the things I have already tried:

1] Changed the ram for a different set
2] Took board out and tried running on a box to eliminate shorts.
3] Tried a different old CoolIT 480watt PSU I have, same problem.
4] Removing all devices except the ps2 keyboard and dvi cable.
5] Tried with onboard graphics and 6950 same problem with both, no difference.
6] Took off my A70 and install stock heatsink.
7] Reset cmos/ changed cmos battery.
8] Tried running with one stick in several slots.
9] Unticked every device in device manager that could wake the computer.
10] Changed every power saving, boot from keyboard, all features I could think off in Bios.
11] Changed the power cord.
12] Changed hard drive.
13] Changed the bios.

Im baffled. Would like to get this sorted as I do love the board. Anyone any ideas or experienced anything similar?