Yes I am experiencing this issue as well. I noticed it when I went to check my voice mail, I would speed dial #1 , it would make the call, but then go into hibernate mode, when it asks me to put in my passcode to check my voicemail, I am unable to bring up the dialpad or any of the interface of the phone. Luckily I get disconnected after no response with tmobile. However if you call someone and you get their voicemail you will need to remove the battery to disconnect from their vm. This does not happen on every call but it does happen almost 50% of the time I make a call either to check my voicemail or call someone on my contact list. I have called HTC and reported this issue with them. They were unable to reproduce the issue. They had me do a master reset back to the factory defaults. But that did not work. So I am getting a new phone sent out to me. Let's hope this new one I get won't act up.