Comment 7 for bug 474175

https://bugs.launchpad.net/ubuntu/+source/vlc/+bug/428884 seems to point to the core issue.

'gnome-screensaver-command --poke' sends a "SimulateUserActivity" message to the screensaver. Checking gs-monitor.c, we find the following:

--- gnome-screensaver-2.24.0/src/gs-monitor.c 2008-08-20 20:53:34.000000000 -0500
+++ gnome-screensaver-2.28.0/src/gs-monitor.c 2009-08-19 18:19:14.000000000 -0500
@@ -231,9 +186,7 @@
 static void
 gs_monitor_simulate_user_activity (GSMonitor *monitor)
 {
- /* in case the screen isn't blanked reset the
- idle watcher */
- gs_watcher_reset (monitor->priv->watcher);
+ /* FIXME: reset the xsync timer? */

         /* request that the manager unlock -
            will pop up a dialog if necessary */

NOTE: I've only included the interesting porition here. The complete diff is attached.

It appears that the mechanism for simulating user activity has been stripped from gnome-screensaver-command. I suspect that the new FIXME is a requirement of getting idle time from Xorg, since the gs_watcher_reset function is no longer present in gs-watcher-x11.c.

I'm going to look into workarounds, since I don't have the expertise to fix this issue myself. If I were a new user encountering this kind of behavior, however, I think I'd be discouraged from using Ubuntu. I strongly suggest that this issue be corrected for Lucid LTS. Otherwise we need to consider alternatives to gnome-screensaver.