I would get your beer as cold as possible (lower temperature = lower pressure) and degas them. I had to do this once with some hard cider that shot across the kitchen when I opened it. To degas, you just take a bottle opener, and ever so carefully pry the edge of the cap up to let co2 out without bending the cap. Go carefully here because if your beer is waaay over carbonated, you could get some raging foam shooting out and losing beer. If your beer is as over carbonated as my cider was, this could take a while and you will need to let only a little bit of co2 out at a time so that you don't get that raging foam. Remember to get your beer as cold as possible. Once you get all the caps off, you could try letting the caps sit on top of the bottles to prevent dust/bacteria from having easy access to the liquid, until the beer is flat. Then try carbonating again. Best of luck to you.