I would suggest that you tell synaptic to force version 1.4.3 and see if that
does it. If that doesn't work I would try to install from source then remove
using the same source script. Also make sure to do a complete removal of the
gnome network manager.

Also you could try googleing the error message about the old uninstall script.
If you can find the uninstall script you may be able to follow it for a manual
uninstall as well.