gsmartcontrol, gparted problems with userhelper and X credentials?

[Eric Smith]

I wrote:
 > Now if I try to launch gsmartcontrol from the Gnome Shell, I get
 > the prompt from userhelper for my password, but it fails to run.
 >  From the command line, the same thing happens, but at least it
 > shows the error message "Gtk-WARNING **: cannot open display: :0".

I withdraw the question.  After rebooting the system, gsmartcontrol and 
gparted both work fine.  I'm not sure what went wrong before.

Eric