I had a great deal of difficulty with Cisco vpnclient 4.6.00.0045; e.g., would not work with a browser with kernel 2.4.31, and would freeze the system when installed with kernel 2.6.13.
The solution, it turns out, is vpnclient 4.7.00.0640; it solved:
- System freeze with kernel 2.6.13 (had to turn off power);
- Browser (Mozilla 1.17.12 and Firefox 1.5) works properly in both kernel 2.4.31 and kernel 2.6.13;
problems with X-term with kernel 2.6.31.
If you're experiencing difficulty with Cisco VPN Client 4.6.x.x, it might be a real good idea to upgrade to 4.7.x.x.