For some reason, emacs functions which use the interactive form don't work for me on Mac OS x. The emacs I am using is from emacsformacosx.com, which up until now has worked flawlessly. An example of such a function that uses interactive (taken from here) is:
(defun multiply-by-seven (number) ; Interactive version. "Multiply NUMBER by seven." (interactive "p") (message "The result is %d" (* 7 number)))
I run it in scratch with C-x C-e, but I'm not able to enter a number and get anything out.