Seems a strange one, never fitted HID's, is there any wiring you have done that might have caused this? Perhaps try refitting the original bulbs if you can and see if it still does it?
Back to my problem, I have been checking around the fusebox in the drivers footwell and found a very small amount of water in one of the connectors (a grey one). Cleaned it out as best I could and so far so good, but won't hold my breath.
Couldn't find any evidence of water coming in through the bulkhead grommet, all wiring seemed dry - had a friend pour water over that side of the windscreen but couldn't see anything coming through.
Hate these kinda faults, difficult to trust the car now, never thought I'd say that about my Lexus