sounds like the space itself isn't a problem, but for some reason some (or all?) requests to internal resources fail. does that sound like an accurate assessment?
if so, my first suggestion would be to logon to the server machine and see if you can access those resources directly in the browser. if so, it might be worth asking for IT help to create a new application pool for the proxy and assign it to utilize a different identity so that you could use a tool like fiddler to inspect the actual web traffic the proxy is spawning to the resource itself.