ArchiMark: You're going to have to enable (remove the #) the "lenny" repository in /etc/apt/sources.list and try again. There may be some fallout when you begin upgrading such fundamental components.
Could those having problems with synaptic please open a terminal and type Code: sudo debian synaptic and post the output here?
sudo debian synaptic
$ sudo debian synaptic sudo: debian: command not found
$ sudo ./usr/sbin/synaptic