Have a look @ this thread.

Someone is suggesting..

Heard that it was something about their "power good" signal that really freaks out 64 boards.

But further down the thread..

have the EXACT same problem but with a K8n Platinum.
it reacts just the same way with my GF4.. But with my Gf2 it works with no problem..
i remember some other guy that had the same problem and he emailed MSI about it and this is what they replied:

Dear Richard Breen,

Having done some research on the issue, we have concluded that its probably
due to a error in the image of the bios.
Provided the component has not sustained any physical damage we can repair
this for 10 P&P which covers the cost of returning the motherboard to you by
courier.


Might it be worth flashing your BIOS cos I can't think of anything else you could try.
It's a long shot, but has to be worth a go.