I can ping, and browse files on the AD Server. But more often than not, the remote server isn't getting credentials properly on login and is using cached credentials.
You need to establish whether this is a connection problem with the VPN / Internet / Routing.
Also check it is not an AD DNS problem; for example:
1. What is set for this remote servers DNS server - I would expect it to have the AD DNS Server set on it's network card so it can find domain specific resources - such as where to login to the domain.
2. If there is a DNS server installed in the Joiners (remote) location where WinGate is installed, can you confirm the following registry entry is set to 0?
HKEY_LOCAL_MACHINE\SOFTWARE\Qbik Software\WinGate\Services\DNS Service\"Startup"