Had one message in the new mailbox. The "1" appeared in the "all" and "unread" slots. Read the message. The "1" still appears in the " unread" slot. Deleted the message, it is still read "1" in the unread slot.
Also, when I click the unread or all slots, it does say there are no messages, and no unread messages.
I figured the staff knows about this bug, thought a discussion thread would be nice, :)
Edied to add: Bug report created. Thanks Kev for the link. :)