[OS X Emacs] looking for help in two areas

[Craig A. Finseth]

I'm looking for help in two areas.

First, if you copy or cut some text (C-W), move somewhere, yank it
(C-Y), the text remains selected.  If you start typing, the text that
you just yanked is replaced.  What is the mode setting that controls
this?

Second, I just upgraded to:

	GNU Emacs 22.3.1 (i386-apple-darwin9.7.0, Carbon Version
	 1.6.0) of 2009-06-07 on scarlett.local - Aquamacs Distribution 1.8c

from a version from several years ago.  With this new version, C-Z
doesn't do anything, even though I have this in my .emacs file:

	(global-set-key "\C-z" 'scroll-down-by-lines)

Anyone have any idea where this is being overridden?  I did some
looking around, and it may have something to do with mouse support,
but I can't figure out (in a reasonable time) how that is actually
linked in.

Thanks,

Craig