Am Sonntag, 20. Februar 2011 schrieb Paul Cartwright:
> On 02/20/2011 01:58 PM, Mag. Dr. Nikolaus Klepp wrote:
> > oh, i overlooked that tart with ":1.0". try this:
> >
> > $ xhost +
> > $ su
> > # DISPLAY=:0 synaptic
>
> # DISPLAY=:0 synaptic
> Invalid MIT-MAGIC-COOKIE-1 key
> (synaptic:10481): Gtk-WARNING **: cannot open display: :0
>
> maybe I should reinstall synaptic..

no, that's not the thing. your X is not running as display 0 nor 1. could you 
make 

$ ls /var/log/Xorg.*

This should give some files Xorg.<a number>.log, where <a number> is the 
display id. that's the thing you pass to synaptic:

# DISPLAY=:<a number> synaptic