Browsing in windows requires netbios and when you go across switches, routers, VPN's also requires that you have a WINS setting on the machine that is doing the browsing.
Normaly this will not matter on a small local network, you don't need WINS because netbios broadcasts even when it's going across TCP/IP.. (Which is nomaly enabled by default as netbios over TCP/IP)
The one thing I do know is that when you throw routers, VPN's and other things in mix netbios doesn't work very well even on TCP/IP..
Now if you just need to map drives and don't really need to browse you should be able to map a drive by putting in the path \machinename\sharename
If you need to browse you may want to add the SME server as your wins server and that should work. (It seems to work for me.)
I am not sure when the VPN in e-smith assigns your IP info using DHCP what all settings it puts in.