Just an update to my post. After I got the randomly recurring shutdowns, my unit developed another major problem. I was driving to work one day and the map screen completely scrambled, the map appeared with hundreds of random intersecting streets drawn over it. I was worried so I reset it immediately, after that I have not had a random shutdown or reset.
I looked back through this forum and I found 4 or 5 similar stories. All were using burned upgrade disks. So I believe it is being caused by the disks not the unit itself. Although it could be caused by the unit having a decreased cap