You are probably running into issues with address resolution. If you're trying to "access the other pc" by UNC path (i.e. \server2\path) you probably didn't setup any way for server2 to find server1.
In a normal closed network by default... windows uses netbios to elect a master browser which can hold the names & ip addresses of servers in the same broadcast domain, and provide them to other peers in the same network that request them. In a virtual hosting service, frequently the servers aren't in the same broadcast domains, and admins go to a great deal of effort to keep the servers from being able to identify each other. It's possible that they prevent netbios all together.
A simple work around... would be to setup a few static entries on both servers using the lmhosts file or the hosts file to provide address resolution. Keep in mind also, that many anti-virus packages might identify messing with either of those files as something bad.