I've experienced this as well, no idea though what caused it. It was fixed by removing tinymce, deleting /usr/share/tinymce manually (some files were still left after dpkg --purge) and reinstalling it.
After this the graphical post editor in Wordpress started working as usual. .m -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org