This error plagues me around every three weeks when I open up my Cisco VPN client on my Mac. The fix for this is straight-forward:

  1. Quit CiscoVPN,
  2. Open Terminal (Applications > Utilities > Terminal), and
  3. Type in the following command: 
sudo /System/Library/StartupItems/CiscoVPN/CiscoVPN restart

Type in your password when it asks you for it, and Terminal should restart CiscoVPN, at which point the error should go away.