Originally Posted by JSanders
JC's instructions above might should also state in #3: After you have copied (or moved) all the contents OFF the Media Card to your PC, delete all the files on the Media Card. You are making sure all the "BBthumbs.dat" files and everything else on the card are removed from the card. It is the "BBthumbs.dat" that seems to be the culprit on the card, as those files were created with OS 4.2, and don't seem to be compatible with 4.5.
So you are placing the card back in your BB as a blank or empty card. Then continue with formatting the card in the BB with OS 4.5 running.
This is why this forum is simply the best!!!
Worked like a charm! I copied everything off, deleted all, and was able to reformat. When I was copying stuff back, however, I thought I was being careful not to copy any .dat system files, but something must've gotten into the bulk copy, so the device started to reboot again. I'll have to figure out what's causing it, but at least now I have a way to get to the baseline.
Thank you, JSanders!