MoBo speaker beeps while using computer

My Abit IC7-G mobo has started beeping while the computer is already running. A while back, I had the hi-lo siren, which turned out to be a fan error from the northbridge fan getting stuck. I disabled it, and that went away. Now, it's making 3 beeps (all the same tone), then a pause, and repeat. The manual doesn't give me a clue as to what any of its beeps might mean... any ideas?