Just got 2008 prius level V Wife took it in and it failed inspection - bad right headlight and left foglight. When she brought it home, the foglight is indeed out- but both headlights are fine. Are these fancy HID lights notoriously intermittent?
Intermittent is the failure mode for HIDs, yes. High-intensity discharge lamp - Wikipedia, the free encyclopedia
Two main components of HID, ballast and bulb. You're going to have to figure out which is giving you the problem. Switch the bulbs from one side of the car to the other. If the right side bulb continues to be intermittent, then it's the ballast. If the left side becomes intermittent, then replace both bulbs. SCH-I535