Did you just put the keg in your kegerator? If so then walk away for at least 2 hours to let the beer settle. Wrenching the keg into your car, driving home and then pulling the keg out of your car and putting it in your kegerator agitates your beer quite a bit and this agitation will cause a short term foaming beer problem. Also, the keg has probably warmed up a few degrees and your kegerator needs to cool the beer back down to the proper serving temperature.