Glad I found this forum....
I got a Droid the day after they came out.... My original droid would spontaneously re-boot, so I took it back for a replacement.
The first replacement that came to me by FedEx had a loose screen, so I sent it back.
Second replacement comes...It looks/feels good, so I set it up, and load my data to it.
IT RE-BOOTS after viewing a picture in the gallery, and then locking the screen with the power button.
I took it to the Verizon store, and the clerk transferred all of my data to ANOTHER replacement phone.
THAT phone re-booted after viewing the gallery, and putting the screen to sleep as well.
I was told it had to be a software issue, and would likely be corrected when the new software update comes out.
I went back into my ORIGINAL Droid....
AND NOW IT DOES IT ALSO 
My original Droid would reboot occasionally, and completely random.
It NEVER used to do it with the gallery/screen lock, scenario.