According to Verizon they are aware of the issue and had this to say:
“It has come to the attention of Verizon Wireless and HTC that customers using the Thunderbolt by HTC have experienced a voicemail notification error with the recent software update. As a result, the update has been temporarily suspended while the companies work together to resolve the issue. Verizon Wireless and HTC anticipate the update being available soon; customers will be notified directly on their devices when it is ready for download."
Apart from the voicemail notification error, it seems that there are complaints about issues over the camera, locking, Google Talk, clock app and even HTC's own UI – Sense. No word on when a new update is expected to roll out, but if you get the notification asking you to update, it looks like you'd be better off running on Froyo 2.2, at least for now until Verizon has officially released a fix.
