Cisco VPN - Fix for Error 51: Unable to communicate with the VPN subsystem

I run Leopard on my Mac and encountered the dreaded Error 51 issue today. The simple fix that worked for me was to run the following two commands as root:

# ifconfig fw0 down# /System/Library/StartupItems/CiscoVPN/CiscoVPN restart
Afterwords, the VPN client started just Error 51.