drove the car to and from work yesterday (45 min. each way). headlight worked fine both ways. BUT (You didn't think it would be THAT easy, did you?)...this has happened before when the car has not been driven regularly in a while. it's winter in NJ so most of the time the car sits in the driveway. if a few decent days come along then the car seems to not have the headlight problem for a day or two. if more successive days of driving are added then the headlight will start to exhibit problems.
it's supposed to snow today so i can't test the car again today. if the headlight issue persists then the next step is to replace BOTH xenon bulbs with OEM ones and see what happens.