Freezing, stubborn phone

[Android Question]

Verizon/HTC Thunderbolt:
I will turn screen on but my screensaver is gone and the screen will not unlock. The screen is black w/the clock showing the time it froze. The standard icons are present as is the half circle I use to unlock screen. When frozen, I cannot turn it off w/the power button. I have to take the battery out. I don't know why it's happening or what I can do to prevent it. Any suggestion will be greatly appreciated! Thank you!

Side note: it's not live wallpaper, just a standard HTC offering that came w/an update.
The freezing is happening more frequently these days. Any ideas???

 

[OutOfPhase]

My suggestion would to do a factory reset.
Go to settings-privacy select factory data reset then hit reset.

You will have to setup your phone again but it should clear up the issues.