I installed the card into a PC and reformatted it using Windows XP. All seems fine now. I'd suggest users not format the 32Gb card using the Droid's built-in format utility.
If you buy Verizon's Sandisk card, it's preformatted. Since it caused unwanted reboots, I formatted it again via the Droid's built-in formatting utility. Reboots continued. So, the formatting didn't seem to matter.
The fix for this problem is to reformat the card using a different cluster size. Once I did this, I haven't seen the problem. I posted all the details on this thread: