There is a service bulletin for Y2K C5's that addresses a problem with the left headlamp door. While it is specifically for a left headlamp door that won't remain closed, perhaps your problem is the mentioned problem in the early stages. The bulletin # is 00-08-42-002 dated June, 2000. If you don't want to return to the dealer, the parts cost is minimal and the bulletin allows 0.5 hrs. for the repair. I hope this helps.