this has been fixed upstream since November, and the fix is already in feisty. The 50 pixel treshold has been changed to 10% of the screen width.
** Changed in: gnome-screensaver (Ubuntu) Status: Confirmed => Fix Released -- mouse movement wakes screensaver https://launchpad.net/bugs/37139 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs