This was a problem that perplexed me for a while too. Ultimately I learned that the curve has several different folders for different email addresses. This also includes a message folder for all messages. First go to the Home Screen and press the menu / Blackberry button. Select "Show All". Now scroll through until you see the offending folder indicating there is a message there. Delete that message and you should be back to normal. My problem had been a saved unread message in the saved messages folder that wasn't being displayed initially. That should take care of your problem!