Just wanted to say thanks to the forums for all of the great information. My (new to me) 2007 IS350 was exhibiting an odd behavior - the driver's side HID headlight would turn on for a second and then turn off. If I tried hard enough cycling power to the headlights, it would eventually get bright enough to stay on. Given another minute of runtime, it would turn off.

I stressed a bit over what it could possibly be, hoping that it wasn't a ballast problem. Read lots of posts here and decided to buy some new Toshiba D4S bulbs on Amazon. Replaced the driver's side bulb this morning and it's behaving fine. The old bulb was slightly hazy near the top, but looked to be an original Phillips bulb with 80,000 miles on the car.

Figured I'd post this for the next guy trying to figure out what's wrong with his HIDs. Thanks ClubLexus

 

This happened to me when the car was still under warranty and dealer replaced the bulb at no cost.