My xenon headlight controller was replaced when the car was only a few months old (previous owner). Since I bought it this summer, I've had problems with one or the other headlights not coming on for a few days, and then it works again. BMW is supposed to replace the controller once again during my next appointment. Are you SURE the bulb is blown? If not, consider the controller problem. I thought my problem was the bulb, until it started working again 3 days after going out.