OK, this is probably a routing setup thing.
In order to browse the computers on a network from say network neighbourhood or Explorer, you need to be able to connect to the
master browser for a network. If you can't connect to a master browser, you will get an error stating that "the list of servers for this workgroup is currently not available" as you are seeing.
The machine acting as the master browser can change from time to time by a method known as
browser elections. This means that sometimes you can browse because a machine that has won the master browser election is able to be connected to, and other times you wont, since the master browser will have changed to a machine that does not have the routes configured for you to be able to connect to it.
This indicates to me that probably on the remote office, the WinGate VPN machine there is not acting as the main gateway to the internet, and that the machines on that remote LAN, or at least some of them have either
a) no default gateway setting at all; or
b) a default gateway pointing to a machine other than the WinGate VPN gateway machine on that network.
if the WinGate VPN machine there is the default gateway to the network (i.e. you are also using WinGate with a normal WinGate license to provide an internet gateway) then simply go to the machines on the remote LAN that you need to connect to, and make sure their default gateway setting in their TCP/IP properties for their Lan Adapters is set to the IP address of the WinGate machine on that LAN.
if you are using another gateway, and you don't want to change the default gateway (that would probably be a bad idea), then you will either need to
a) manually add a route entry to the route table on the machines you need to access; or
b) install or enable a RIPv2 client on the machines you need to access. This is the easier option, since it will then configure the route table automatically depending on advertised routes from the WinGate VPN machine.
We wrote a RIPv2 client specifically for this purpose which you can find on our website
http://www.qbik.com
Make sure that whatever you do, that you don't install the RIP client on the VPN gateway machine.