I think I'll just paste in the email I sent to MSI, hoping for the chance that someone's seen the same thing before:

I recently purchased two brand new MSI motherboards (MS-6380, as shown here http://www.msi.com.tw/program/produc...&MODEL=MS-6380) and have been having a few troubles with the both of them.

Everything seems to work fine, until you either try and exit the CMOS screen, or you try a soft boot via CTRL + ALT + DEL. When this happens, the system will just stop. Looking at the diagnostic LEDs on the board gives various reading, depending what happened. You cannot reset the board or use the power button. I found the only way to get it working again is to disconnect the power for about 10 seconds.

To make sure it was nothing else, I've tried replacing video card, CPU, RAM, PSU, case, having no drives, having 1 or 2 drives and so on, and in the end flashed the BIOS with the latest update in hope that it would work. But no.

I then had a look around the internet to see if other people had the same problem, and the best I could find was what had happened to a series of Epox boards, talked about here (http://www.overclockers.com/tips710/). This is what lead me to try a BIOS flash.

Any ideas / help on this would be most appreciated.