latest CVS on OS X: mouse wheel no longer works?

[fortepianissimo]

This started I think since a week or so ago on the CVS version of Emacs
running on OS X 10.4.3 (Emacs version 22.0.50).

When I scroll my mouse wheel now, instead of scrolling the content of
the window, I got a bunch of error messages in the status bar:

<wheel-up> is undefined
<wheel-down> is undefined
<double-wheel-up> is undefined
<triple-wheel-up> is undefined
...

Does anyone know how to work around this? (and what has changed?)

Thanks a lot!