Connecting to VPN (Mac OS X) I'm trying to connect to VPN on Mac OS X via several ways:


Native vpn client (doing something like this:
https://www.publicvpn.com/support/MacOSX105.php)
By Anyconnect vpn client
By Cisco vpn client


In 3 case I receive the 51 error and I read, that it's ok for mac. 
In 1 case I recieve no errors, just can't connect. 
In case 2 I receive error message: "the vpn server did not respond", but ping to vpn server I try to connect is successfull. 

What I'm doing wrong? When I tried to connect in Windows by cisco vpn client, connection was successfull. Can the problem be in that the vpn is based on windows?
The Cisco VPNClient app is not officially supported in 10.8.  You may have some luck by using Java Preferences to specify the 32-bit JVM and either disabling the 64-bit or changing it to be secondary.  

You're better off replicating the settings from your Cisco configuration into a new native VPN (IPSec) connection.

Look for the encrypted Group password in your .pcf file, then head over here to get the decrypted value.  After that it should be fairly obvious.