I have an '06 Commander and recently there has been a "NAV message" stating that there is problem reading the NAV DVD. I have taken it out multiple times to clean it and it seems to be a quick fix, but 1-2 days later, the message reappears. Unfortunately, the message is accompanied with a rucurrent alarm that will not stop, no matter if the NAV is activated or not. Anyone experience this or know how I can fix it? Thanks.