Gap access Active Directory with VPN tunnel

Hi,

I've make a ipsec VPN tunnel from two Fortigate 60D with this video tutorial

http://video.fortinet.com...-w-overlapping-subnets

the vpn connection is ok and the ping from the two lan work correctly but I wont to connect some client to the active directory.

I'm not able to connect the client to the windows domain controller; the client have the primary dns with the ip of the windows domain controller and the ping from client to this work pefectly.

in other the access to the server data work: if in the client go to start -> run -> \\server  or \\ip-server

and digit the domain credential, I've the access to the share data of server

why the registration of client in the domain not work?

tnks