- Install the "patch" tool if you haven't done already, eg. run "sudo apt-get install patch".
- Download the client: http://tuxx-home.at/vpn/Linux/vpnclient-linux-x86_64-4.8.01.0640-k9.tar.gz to whatever location.
- run "tar zxvf vpnclient-linux-x86_64-4.8.01.0640-k9.tar.gz"
- Go to the new dir, eg. "cd vpnclient"
- Download the patch that matches your kernel into the directory where your vpn client was extracted. In my case: http://projects.tuxx-home.at/ciscovpn/patches/vpnclient-linux-2.6.24-final.diff
- Run "patch < vpnclient-linux-2.6.24-final.diff" in the directory where you extracted the vpnclient.
- Install the vpnclient by running "sudo ./vpn_install" and follow the instructions.
- Start the vpn client: "sudo /etc/init.d/vpnclient_init start"
Once everything has been set up, use "sudo vpnclient connect <your-vpn-profile>" to connect to the VPN.