Comment 1 for bug 405543

Let me add that I see the very same problem here with our SunRay Server System which we have running under Ubuntu 9.04 (Jaunty). Since we have installed updates and rebooted all SunRay sessions can't be locked anymore. After some short investigation we see that "gnome-screensaver" isn't automatically started anymore. And upon manually starting it and invoking the screensaver we can't unlock the screen anymore because there appears no dialog.

When manually starting the dialog we also received the following X error:

-- cut here --
The program 'gnome-screensaver-dialog' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadClass, invalid event class'.
  (Details: serial 269 error_code 133 request_code 131 minor_code 6)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the --sync command line
   option to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)
-- cut here --

However, when logging into the system via a remote X connection rather than using the local SunRay displays gnome-screensaver comes up find and alslo gnome-screensaver-dialog works as expected.

So there seems to be really a problem with gnome-screensaver lately.