On a WebCrossing server running SSL only, we don't seem to be able to access XML-RPC enabled functions remotely. If we set the server to respond to http requests it works, but if we run SSL only there is no response.

If the XML-RPC request is from a WebCrossing server, and is to an https URL, web crossing will encrypt it.

But if you're only using webx as the server not as the client, then it is your responsibility to make sure the connection from the client is set up properly (encrypted) to the server.