I've also seen this behaviour with network-manager-vpnc - if network-manager-vpnc-gnome is installed without network-manager-vpnc, then you can't configure a Cisco VPNC connection. Installing both packages fixes this, so the -gnome version should probably be dependent on the main network-manager-vpnc package.
I've also seen this behaviour with network- manager- vpnc - if network- manager- vpnc-gnome is installed without network- manager- vpnc, then you can't configure a Cisco VPNC connection. Installing both packages fixes this, so the -gnome version should probably be dependent on the main network- manager- vpnc package.