I cannot to several workstations on a network at a remote site. The fact that I can connect to some indicates this isn't a routing problem, or a firewall problem. The error message is the standard one you get when Remote Desktop is turned off, but I checked this setting when last visited the site, and it was on.
I can't think what the cause could be.
I'm using IPSec to tunnel to the local network and using local IPs from the DNS list.