“Empty Page Title Not Handled in Menu System” seemed to cover what I found about five months ago (as of this writing according to the WordPress Trac system). Simply put, if you had a page without a title and you used that page in your WordPress navigation menu you could expect to have some issues with its display.
Several comments later; a commit by Mark Jaquith today; and, these issues are well taken care of now … cool! I’m happy to have been part of the process.