Lion clients unable to connect to Snow Leopard server

If you are attempting to connect from a bound Lion client to a bound Snow Leopard server you must use the FQDN for the server. 

For example:  myserver.test.network.com

If you do not you may receive an error that says "The version of the server you are trying to connect to is not supproted.  Please contact your system administrator to resolve the problem."

Also check what authentication method you are using.

• Open Server Manager
• Highlight "AFP"
• Click on the "Access" tab
• Change "Authentication" to "Any Method"

Attempt to connect from at Lion client using the FQDN of the server.

Note: changing the authentication to Any Method can possibly break single-sign-on for Snow Leopard client.  If this happens change the authentication to "Kerberos".  Lion clients should still be able to access the server.