Hi - I am about to buy a 07 certified M35 and have heard several people have problems with the navigation. I know I probably won't even know how to work it when I test drive the car. Some people have found that the antenna was installed upside down at the factory - but you would think with a certified car they would have found this by now! Good luck with getting the problem fixed. Did you get the "Elite" warranty, sometimes called a "wrap" warranty? Good luck!!