If your Cisco VPNClient application will not launch. Maybe it's throwing up "Error 51: Unable to communicate with the VPN subsystem." and you don't want to take the time to restart your Mac to fix the issue (or maybe a restart doesn't fix the issue!) then try this...
- Open Terminal and type: sudo kextunload /System/Library/Extensions/CiscoVPN.kext
- After authenticating type: sudo kextload /System/Library/Extensions/CiscoVPN.kext
- Quit Terminal and launch Cisco VPNClient!