Comment 3 for bug 614248

I am seeing the same problem: gnome-power-manager crashes immediately on launch with this message:

(gnome-power-manager:3662): GLib-GObject-WARNING **: /build/buildd/glib2.0-2.25.13/gobject/gsignal.c:2275: signal `proxy-status' is invalid for instance `0x9274d30'

Gdk-ERROR **: The program 'gnome-power-manager' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadAtom (invalid Atom parameter)'.
  (Details: serial 161 error_code 5 request_code 150 minor_code 15)
  (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.)
aborting...

However, when I relaunch gnome-power-manager from the terminal, it asks for a password to run gnome-power-backlight-helper. If I refuse the password, gnome-power-manager does not crash (though it does still emit the proxy-status warning)