Try the  vpnclient-winx64-msi-5.0.07.0440-k9.exe version instead. See my entry in the thread below confirming that this version works on Win7-64 with Dan Costa's steps in the thread below.

I was getting the "Installation ended prematurely because of an error" message when clicking Next in the installer. Step 5 in the above solution fixed the installer and I was able to successfully install and use the VPN client. (I installed with vpnc...