zapping out of ledit

[cent at MIT-AI (Pandora B. Berman)]

i was hacking xlisp/ledit, supduping from cadr7 (all right, i know i'm
ignoring the wonderful facilities i have access to on cadrs by hacking
maclisp, but that's not the issue). 
whenever i tried to save a function in the ledit buffer to read into
the lisp when i returned there, by typing M-z, which is supposed to do
that, the screen flashed and otherwise ignored me. i had to use alt-z
to get my functions saved up for perusal by the lisp. is this maybe a
bug with the new keyboards (there is one on cadr7)?