This same behavior is present in the latest Emacs pre-release

   GNU Emacs 23.2.91.1 (x86_64-apple-darwin10.4.0, NS apple-appkit-1038.32) of 2011-01-02 on oatmeal

on

   Darwin oatmeal 10.4.0 Darwin Kernel Version 10.4.0: Fri Apr 23 18:28:53 PDT 2010; root:xnu-1504.7.4~1/RELEASE_I386 i386