VPN issues Cisco IPSec Mavericks 10.9.3
To use the Cisco VPN Client, the following network ports must be opened in your firewall software:


500 UDP
4500 UDP
10000 UDP


Normally, When you install the Cisco VPN Client, it automatically opens these ports on the firewall. So check whether the user has another software firewall installed on the computer, If so you will need to manually open these ports.

Hope it could help.