This is a very strange (and interesting) bug which started happening after July's big FTP update.
Hands importing, HUD (Tournament Default) running, the chat window is detached. I click on the Note Editor button, write a note, save the note. The HUD refreshes (whether because of the save or because it's just time) but when it comes back up it's overlaid on the chat window instead of the table window. If I get rid of the detached chat window than the HUD does the right thing and redraws itself on the table window. Then I can detach chat again and everything is fine (as long as I don't add another player note).