I asked my hosting service to look in to this and this is what they replied to me...
"We have seen this before, basically what you have to do is delete the messages and give it a minute or so before you clear the deleted items folder. If you do it too quickly the BES server doesn't get a chance to scan the mailbox and note the change in status. This will resolve your issues."
I don't know if this is going to work. I typically delete messages all day and only empty my trash a couple of times a day, but we can work on it.