I just finished building my system based on Gigabyte's GA-990FXA-UD5 motherboard. Sporadically (most of the time), a medium-pitched, annoying tone comes from the system speaker. It comes on and off with various system activities, but it's impossible to identify just which ones cause it. I've "band-aided" a fix by unplugging the speaker. Any idea how to actually fix the problem? Thanks.