Comment 26 for bug 528094

Thanks Nadim.

I have upgraded now to Lucid on a new machine, and the bug is still present. I did notice that Ctrl-Alt-L locks the screen with xscreensaver now :)

I tried to fix the DBus issue, but I am in the same boat as far as knowledge about what's happening there. In
https://bugs.launchpad.net/ubuntu/+source/indicator-session/+bug/436724
Ted Gould says that what the session menu does is:

$ dbus-send --print-reply --reply-timeout=100 \
--dest=org.gnome.ScreenSaver / org.gnome.ScreenSaver.Lock

so I tried that on my machine. It did not work and the response was:
Error org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.ScreenSaver was not provided by any .service files

I made a file at /usr/share/dbus-1/services/org.gnome.ScreenSaver.service with the following contents:
[D-BUS Service]
Name=org.gnome.ScreenSaver
Exec=/usr/bin/xscreensaver

(The default has /usr/bin/gnome-screensaver instead, I changed that hoping it would call xscreensaver.)

Tried that again and it still didn't work:
$ dbus-send --print-reply --reply-timeout=100 \
--dest=org.gnome.ScreenSaver / org.gnome.ScreenSaver.Lock

Error org.freedesktop.DBus.Error.Spawn.ChildExited: Launch helper exited with unknown return code 1

I went through this on Karmic as well, same result. If there was someone who knows more about how DBus works, maybe we could get a workaround. It seems to me that there is something missing other than the .service file. The --dest now seems to be there since the .service file is created, but I don't think anything will understand the message name, which is "org.gnome.ScreenSaver.Lock"
("destination object path" = "/" and "message name" = "org.gnome.ScreenSaver.Lock" according to the dbus-send manpage.)