Nav System Doesn't Recognize the Map DVD

[Z '07 Tundra]

Greetings from North Texoma...

I have had my Tundra since Aug 07 and have recently begun having a problem with my OEM Nav system and the OEM DVD that came with it.

Has anyone else out there has had their navigation system "reboot" itself when you first start up your truck. The first screen that pops up says "Map DVD not detected" (or something to that effect)...Unfortunately, the map DVD is already inserted, has always been inserted, and was never ejected. Without any additional actions by the operator, the system then proceeds to reboot itself, and then begins to function correctly. Problem is all the user-specific data (road speeds, map displays, etc.) then have to be reset. Another problem is nothing connected with the nav system display (radio (AM, FM, or XM radios, back-up camera, etc) functions untill the system has completed it's reboot...

Oh, and in true automotive fashion, did I mention the fact this happens sporadically, and for no specific rhyme or reason? One constant seems to be connected to how hot it is outside, although I've also had it happen after the truck has been sitting, untouched, all night long...

I'm scheduled to take 'er in to the dealership on Monday, but was hoping a few of you out there may have heard or experienced similar symptoms. In the spirit of anticipating what the dealership might say, does anyone out there have "tech manual" guidance on the care and cleaning of the DVD reader? Can you use the same type of process as you might use on a DVD player in your home entertainment system?

Any words (be nice!) would be appreciated...

Z