As evident by your actions so far, you need to get some sense of wheter your problem is from a bad DVD or something wrong in your head unit. IMHO the easiest route is to see if it's the disc. You've tried some of that, but it would be great to try a disc that's know to work already. The first option would be to borrow one. Maybe your local Jeep or Chrysler dealer could be of service in that regard.
The next option: you could either buy a new DVD from Chrysler for about $199 (ouch) or go to eBay and get one for about $21 (yeah).
I bought from eBay seller "ofrb1". Given that you already have a licensed DVD, IMHO I see no problem buying one like this on eBay. Just pay attention that you get the right one for your head unit, which is likely the "REC" model.
His DVD is also "motion unlocked" so that you can set destinations while the vehicle is moving. The factory software normally inhibits that if you're traveling faster than 15 MPH. Of course, you'd probably want your passenger to be performing any navi destination settings while you are focused on driving.
If I recall correctly, his DVD is the "AF" version. His ad does not state that, but that's what I received.
Chrysler and Navteq recently announced an AG version for the bargain price of $199. When will they come to their senses and figure out that their price is ridiculous? Aside from the vehicle integration, the in-dash navi does not typically compare well with a Garmin/TomTom/Navigon/etc. that you would get for that $199 check.
http://www.jeepcommander.com/forums/showthread.php?p=84746
