They're not vents, its just where the aluminum is designed to break when the caps pop.
There are lots of places on the net that you can search for that will do a complete re-capping of your motherboard for a good price, and use good quality caps.
The problem stems from the Chinese stealing the formula for the capacitors internal liquid, but they either didn't make it right, or got a bad formula, so there was a period of about 2 years where damn near every motherboard manufacturer used these "bad" caps on their boards. Some manufacturers have stepped up to the plate like Abit, and will fix them for free no matter how old the board is (they used to at least). Some manufacturers had class action law suits brought against them an settled our of court.
The first step I would take is contact the board manufacturer, but only after doing a bit of research so you sound knowledgeable about the bad caps. If it's one of the big boys, they may say sent it to us, and well fix it for free.