Question : Problem: Cisco VPN ERROR: Authentication Rejected: Clock skew greater than 300

I am trying to configure ASA VPN using Windows AD authentication. When the VPN client tries to connect the VPN, it receive Reason 413: user authentication failed. If I use test aaa authentication command, I receive "ERROR: Authentication Rejected: Clock skew greater than 300".
My configuration can be found this link: http://www.howtocisco.com/cisco/samples.htm.

Any suggestions?

Answer : Problem: Cisco VPN ERROR: Authentication Rejected: Clock skew greater than 300

What are the clock sources for both?  Try using the same NTP server for both and see if that help.  Authentication can break if they are too far out of sync.

Cheers,
Gary