[Shotgun!]

OMG, what have you done? If the car is flexing that much you have two options: get a cage or scrap the car. The fact that it's not happening to the other door means it's prolly not the car flexing. Is teh window motor assy. pushing the window up too far? Or do you need to work on the door? Take careful note of how the door itself is fitting against the car. Do you notice high amounts of wind noise at 65mph+? My bet is that it's the window motor screwing you. Get in touch with niteryder...or however he spells it. He won't do it for ya, but he will tell you what a bitch it is.