(Mmmm..user interfaces are a particular love of mine, so be warned, I will probably post a lot.)

Thoughts and ideas about the chatterbox:

• Have it float to the top when you have a personal message.
• Have it float to the top when "active."
• Have a different font color for personal messages.
• Put a "how to" link next to the "Chatterbox" title that goes to a well written intro on how to use the chatterbox, especially on how to msg people.
• Is there a way to check off your personal messages without clicking "talk?" Should there be? Perhaps rename "talk?"
• Allow the chatterbox to open as a separate full screen node, showing a larger history of recent talks, and allowing more control
• The ability to block certain users from talking to you (hopefully, never be needed, but history says otherwise)
• In the full screen mode mentioned above, allow an optional META REFRESH
• Keep the most recent talking longer. I have many windows open and often miss some of the dialogs.
• Have a red line appear (or some other marker) that appears right below the latest "post" you've read, when it gets busy.
• Allow a way to see recent messages that have disappeared - perhaps by invoking the full-screen mode. However, I would not advocate having an "archive", i.e. don't allow seeing conversations that occured when you were not logged in, as they tend to be very topical and transient.
• Perhaps maintain a log of your private messages.