I just helped Michelle get her Cisco VPN Client to work after she got an “Error 51” asking her to ensure that she at least one network adapter enabled (which was the case). The client software wouldn’t even startup to let us configure anything. After a couple of calls to tech-support, finding out that the error isn’t explained in the manual and a re-installations we found the following to work: disable the Firewall and Virus-software (McAfee in that case; make sure your machine is still behind another firewall, e.g. your routers’ firewall), go to the Control Panel > Administrative Tools > Services. Then stop and restart the “Cisco Systems, Inc. VPN Service”. The startup setting should be set to automatic BTW.

I still don’t quite understand why this works (Shouldn’t the client communicate with the service using named pipes? Shouldn’t the firewall be irrelevant for the startup of the client?), but hey…

Please leave a comment if that worked for you; or whatever workaround you found. Thanks.