join windows domain over vpn ipsec tunnel

Greetings, I have an ipsec interface mode vpn tunnel between a fortinet 60' s and 1000a. Everything works great except one thing. A pc at a remote site cannot join a windows domain. Once the pc is joined everything else works, including domain login and share access. I tried turning off all protection profiles on both ends and that did not work. Services on both ends are set to " ALL" Also, this is a non active directory domain and remote pc' s use an lmhosts file. This worked great when we were on frame/relay. But since the change to internet/vpn this has been an issue. So if I join a pc over the tunnel, no luck. Move the same pc to local net and it works. I' ve been fighting this one for a while so any help would be very much appreciated!!! Thanks!