How long is your beer line? How long has it been kegged? Are you using cobra taps or faucets? And finally, what temperature is your beer in the keg? That will all help determine the cause of the foaming.
I have kegged 4 other batches without this problem. temp at 42 deg and line is 3 feet. it seems that there is air getting into the line. I see bubbles in the line.