Note: This forum post is a bit outdated and is locked. The file that it refers to has been renamed. This method works for me on Natty.



To de-clutter the Gnome screen lock option for "Leave Message", open Terminal and type the command:
Code:
gksu gedit /usr/share/gnome-screensaver/lock-dialog-default.ui
Then, find the line that says
Code:
<object class="GtkButton" id="auth-note-button">
and edit the next line to say "False".
Note: It's case sensitive.