Gnome Network Manager VPN Tab Disabled on linux

I've the NetworkManager service is installed and started under Linux desktop. The applet is running. The NetworkManager can display available network hardware and wireless networks. But, I'm unable to add VPN support as the Add tab is greyed out. I need to use both PPTP and Cisco vpn clients. How do I fix this problem under Debian or Ubuntu Linux?

The Gnome NetworkManager has pluggable support for VPN software, including Cisco compatible VPNs (using vpnc), openvpn, and Point-to-Point Tunneling Protocol (PPTP). You need to simply install the NetworkManager VPN plugin and configure the user's machines with the VPN's settings. The first time they connect, the user will be asked for their passwords.

Fig.01: Gnome Network Manager Cisco PPTP VPN Connections

The Add tab is greyed out when required plugins are not installed for Gnome NetworkManager. The following plugins should be installed under Debian / Ubuntu Linux:

1. network-manager-openvpn and network-manager-openvpn-gnome - network management framework OpenVPN plugin GNOME GUI
2. network-manager-pptp and network-manager-pptp-gnome - network management framework PPTP plugin GNOME GUI
3. network-manager-strongswan - network management framework strongSwan ipsec vpn plugin
4. network-manager-vpnc and network-manager-vpnc-gnome - network management framework (VPNC plugin GNOME GUI)

To install all of the above plugins use the apt-get command as follows:
$ sudo apt-get install network-manager-openvpn network-manager-pptp network-manager-vpnc
The following plugins should be installed under RHEL / Fedora / CentOS / Scientific Linux / Red Hat Enterprise Linux desktop systems:

1. NetworkManager-openvpn : NetworkManager VPN plugin for OpenVPN
2. NetworkManager-pptp : NetworkManager VPN plugin for pptp
3. NetworkManager-vpnc : NetworkManager VPN plugin for vpnc

To install all of the above plugins use the yum command as follows:
# yum install NetworkManager-vpnc NetworkManager-pptp NetworkManager-openvpn
Now, you can add vpn connection to your system using NetworkManager itself. You may need to restart the NetworkManager as follows:
# /etc/init.d/network-manager restart