{begin totally unrelated story} When I was in an electronic repair class, this idiot put capacitors in each socket on a long AC power strip, then plugged it into the wall. It was a very interesting experience -- about had a heart attack -- because I wasn't expecting it. {/end story}
Back to your topic:
I have read a few articles on your issue, because I had a friend with the same problem. Do you know if your MB is [was?] ABIT, MSI or something else?
here are some links that may help: [had them bookmarked for my buddy.]
http://www.abitsettlement.com/
http://www.pcstats.com/articleview.cfm?articleID=195
http://theinquirer.net/?article=17075
They must have been buying cheap ass caps to cut costs, who knows. good luck though. I'd just replace it and then try to bitch your way into a refund or replacement.
Josh