Originally Posted by klepow
When I try to start Synaptic, or Update Manager, from the GUI, I get a message in the task bar saying "Starting Administrative Application" for a few seconds then It disappears, and nothing else happens.
The task bar message does disappear after a few seconds, even if the application is still starting up. It might help to open a terminal and run top, and press “u” then enter your username (to filter out everyone else's programs), and see if the process is still running.
If you can start it from the command-line but not from the icon, then the icon must be doing something different. Try this: Right-click on the “System” menu, and click on “Edit Menus”. Find the Synaptic Package Manager icon, and right-click on it and select properties. This will open the launcher dialog for the Synaptic icon. Make sure that the “Command” in the dialog is the same as the program you are running from the command-line.
Either way, I would try running it from the command-line, with exactly the same command as the icon, and top running in another terminal, and see what happens. Hopefully, we can get an error message out of it.
Klepow suggests re-installing. If you are going to go that far, then I would start by deleting the .gnome and .gnome2 directories from your home directory, and logging in again; that will reset your menus (and many other settings) to the defaults, and is a lot less disruptive than a complete reinstall.
Hope that's of some help,
—Robert J Lee