Gah! You can save a lot of trouble by using the level tool upstairs.
*pokes FrickinIdjit for being rude*
This isn't the first time I've mentioned this method on here of replacing the wayward ceiling tiles, and yet you are the first snippy reply I've gotten to this. My method does work, even though it may take a few precious minutes of time to do so. If you do have another way that works, speak up and offer some more details on how to do it and actually be of some help instead of wandering in rudely and making such snide remarks like everyone should just know what you're going on about.
And maybe that's not even Morague's problem either. Do you have any other ideas what it could be? I expressed my opinion based on the few times I've had lights not working. If you have a different experience to share, that would be most helpful in diagnosing the problem and finding a solution.
Morague, whatever it is, I do hope you get it sorted out.