Thanks, I accidentally started my phone in safe mode because I had read somewhere about powering up with the vol-down button pressed. While in safe mode I uninstalled a number of apps, including the Forest HD Wallpaper and the Transparent Clock and Weather.
When I restarted the phone was acting just as bad so I figured I'd have to pay a visit to the Verizon store today. I powered it down.
Late today, after a marathon sleep-in, I powered it up just to see what would happen and it was running fine!
I reinstalled most of the apps I had trashed, including the Forest HD Wallpaper with no problems. Then I reinstalled the Transparent Clock. So far so good. As I started to change settings for the clock the problem reappeared!
It appears that one of the settings I chose causes the clock app to behave very badly. I've deleted it but I think I'll reinstall it and verify exactly which setting seems to screw things up - then I'll notify the app author so he can fix it.
Thank you for your answer. I'm glad I found this forum.