[slime-devel] M-. can't find definitions

Hello, I'm a relatively new emacs and SLIME (for lisp) user. I have set up a checked out version (as of a day ago) of SLIME in my emacs and it seems to be working well. However, whenever I use M-. to go to the definition of anything, I get: "No known definition for: <thing-at-point> (in <package-name>)" in the minibuffer. How can I fix this? I don't understand what I have to do to make this work. Thank you. -pete