That clue would have me get out the Volt meter and see what the CMOS Battery is reading. http://www.asus.com/Motherboards/SABERTOOTH_990FX/ clearly shows the ubiquitous CR2032 so you want 3 or higher volts. Many boards halt when that's too low.

The clue also tells me to look again at the power supply. It could be worn out from working hard. The machine details are slim but I'd like to read that some 600+ Watt Single RAIL PSU was used.
Bob