Car heats up, one headlight goes out..

[Ricochet]

never did this until I installed the hid's. I'll be driving on the freeway (getting airflow I guess) but when I get off on an exit, my driver's side light flicks out. When I turn the car off at the store or whatever and come back out and start the car back up, turn the lights on, they both come on normally. My car doesn't overheat or anything it just gets really warm under the hood after driving a little while. I have both ballasts mounted in open areas under the hood, I wonder why only one turns off?