I have a 2004 BMW X5 and the sat nav is showing an error. Have cleaned the laser, cleaned the disc, tried the DVD unit in another BMW and it works fine! But I still have an error message pop up when I try and access the sat nav.
Try performing a battery disconnect. You have to remove the spare tire and the cover over the battery. Wait at least 5 minutes after the key is shut off before disconnecting battery negative. Once you have disconnected the battery leave it disconnected for about ten minutes. This will re-set all of the modules. Once you have re-connected and started the vehicle turn the steering wheel lock to lock and the abs lights will go out. Now check the function of your Nav system.