I wasn't thinking of an app because it sounded like it was working prior to being put in Silent mode, but your comments made me think of trying it in Safe Mode and seeing if it works then. It will boot the phone without your apps and it would let you know if one of them is the problem. FoxKat's written about it but for the life of me I can't seem to get the forum's search function to find where! So here's a link on Verizon's site telling you how to do it.
Good luck!
It's a sticky now thanks to SmallTownGirl13.
http://www.droidforums.net/forum/showthread.php?t=200128
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