Well, if you are using your original BMW map DVD, then I’m taken aback.

I guess a long time to load means more than four or five minutes at least, or not loading at all on occasions. If that is the case it could certainly be a dirty or misaligned lens or a dirty or scratched disk. I would try to read the DVD in my computer. In fact I would try to protect my investment saving an ISO image to hard disk and making a backup copy. A copy may perform better, in spite of all said above, if your original is really that bad.

If the DVD is new or you are still under any sort of warranty I would run to the dealer with the problem. If no warranty then I would keep well away from dealers, unless you know a very honest and skilled one. Try cleaning the lens or try a different map DVD, outdated, if needed be (should make no difference). Try upgrading your software as soon as a newer release is available (you can not reload the same release and downgrading has secondary effects you may not want). Try disconnecting the battery for about 15 or 30 minutes, to ensure a system reset. None of this is guaranteed to sort your problem out, but then the system is moody, as I said, and your problem may go away without you ever knowing why.

Regards and good luck.