I think what you’re describing is what happens when you don’t follow Andy’s instructions to open the link in a new window. If you open the link from within a frame, it’ll open the chat page within that frame, leaving the original chat in it’s original frame, and you’ll end up with a chat frame and forum frame within what should only be a forum frame. This doesn’t cause a problem if you don’t follow the instruction initially, since we’ve essentially got one frame operating as default on the forums, but when you open it twice or more, like a muppet, you’ll have trouble.
Oh and you can’t close the chat frame while on the test chat page.