Started about a week ago after deleting a large quantity of emails. My inbox shows a quantity of 1 - "Inbox(1)" - unread emails as well as everywhere else - bottom of the mail screen and on the start page. I've no filters keeping me from finding it. All my other folders are empty. Tried hard and soft reboots, pulling the battery, etc.

its the system email from when bb connect was registered. this is what you need to do. go into your email then click menu then goto then system. thats were the emails are for the bb connect reg. hope this helps. send me a pm if not.