While tracking down an emacs problem, I noticed the following while compiling emacs:
Dumping under names emacs and emacs-21.3.1 715504 pure bytes used ./emacs -q -batch -f list-load-path-shadows This site has duplicate Lisp libraries with the same name. If a locally-installed Lisp library overrides a library in the Emacs release, that can cause trouble, and you should probably remove the locally-installed version unless you know what you are doing.
/usr/share/emacs/site-lisp/tree-widget hides /usr/share/emacs/site-lisp/slime/tree-widget