I recently gave an ambigous class name to jde-open-class-source, and was presented with a dialog box that was missing OK and Cancel buttons. The problem occurred in current cvs as of halloween with `21.4 (patch 12) "Portable Code" XEmacs Lucid'. I'm not inclined to look into it myself, now that I see how easy it is to replace the dialog with a call to completing-read.
Jason
