I've been having a problem that may be similar; I've begun to think it's related to the battery--my BB shuts down when I'm on a call that lasts over 5 minutes or so, or when I download an app, or anything else that makes the phone work particularly hard. Let me know if you think it's something similar. I've ordered a new battery, and hopefully I don't need a new phone--wiping and reinstalling, etc, has done nothing.