I have a, possibly related, problem with this board as well:
Even though the CPU fan is fine (I've tested it in other systems), on system boot the board seems to detect that the CPU is cool, and so doesn't spin up the CPU fan. This in turn causes the system alarm to beep constantly at boot because the CPU fan isn't spinning.
If I power the system off and on (so that the CPU is still warm) or leave the system to warm a little, then the fan starts to spin and the alarm stops.
Neither turning off Cool & Quiet or CPU fan-speed monitoring seems to be a good option. All other systems I've encountered briefly spin up all fans to full speed on boot - why doesn't the MA790FXT-UD5P?