ok, let me start by asking this. when you re-did the headgasket the last time did you start the car and just let it sit and run for AT LEAST 20 mins? that is the proper way to get a headgasket to seal. let the car idle and go through a few cooling cycles with the fans and such. this way it warms up slowly so the headgasket can “seat” itself. if you dont do that its probably what caused this to happen again. that or the head was warped and you need to have it re-trued