I've found that when Spell Check is turned on in the editor, and you highlight a word that is misspelled, if the page has been scrolled down at all, the pop-up box that contains the suggestions moves proportionally higher on the screen.
I didn't see anything filed in the Trac, so I filed Ticket #19105. I apologize if I shouldn't have filed a ticket first, but I was fairly confident that it wasn't a duplicate.
