Am Sonntag, 20. Februar 2011, um 15:25:39 schrieb Paul Cartwright:
> in a super-user terminal I get this:
> # synaptic
> Invalid MIT-MAGIC-COOKIE-1 key
> (synaptic:19493): Gtk-WARNING **: cannot open display: :1.0
> 
> in a user terminal I get this:
> $ synaptic
> bash: synaptic: command not found
> 
> from the debian menu, clicking synaptic does nothing.

try this:

locate synaptic

if it isn't found anywhere, it has been uninstalled (probably).
you can get it back with

aptitude install synaptic

(as root, obviously)

werner