Detailed instructions (and feedback with alternatives) here:Solution to Reason 442: Failed to Enable Virtual Adapter with Cisco VPN Client on Vista x86
that page says
Update: This problem has been fixed in Cisco VPN Client 5.0.03.0530. Please speak to your Cisco supplier to obtain this new version. When disconnecting from a VPN connection it appears the new client performs these actions for you automatically (it takes around 60 - 90 seconds now to disconnect from the VPN session). I am unable to redistribute the client from this site - please speak to your Cisco supplier / IT Team.
but I am using 5.0.05.0290 and encountered the same.
I just got connection to work (after just getting the lient and the necessary group VPN), so haven't had a chance to see if it recurs, and if the solution works again.
If problem persists, I may try the registry hack too.
Those instructions worked for me,
but I had to reboot as in step 7 of this shortened version of the above instructions.
Others say you have reboot the interface more than once, so perhaps doing that is what fixed it, and not the reboot... no way to tell.