I have the same problem. The lifter blocks are shot and the dealer will tell you that the entire cassette will have to be replaced. You are looking at a thousand dollars minimum. I tried the fix posted by Nathan Davies at www.nathandavies.net but I could not get the sun roof panel to slide back. Apparently, it is a common problem among older E-36 cars. I have decided to leave it till spring next year before dealing with it again. Anyways, if you are mechanically inclined, you could get a used sunroof casette with all the necessary parts for $350. Check out www.vinesbmw.com. Good luck.