I'm totally guessing here (based on your small description and error message) but if you're trying to run full integration testing (where your silverlight tests talk back to a remote web service (RIA Services?) Unless you are running a specific web server
to host RIA services, and you configure your test xap to talk to it - you're stuck (without making changes on your side to support this).
Your test application (when run under StatLight) is running in the context of the StatLight host silverlight application. "Home base" in this case is the StatLight web server, which only exposes StatLight specific web methods. So if you have something
trying to talk back to "HomeBase" the location it came from - you will run into issues.
I did, however recently make a change to demonstrate how you could possibly run StatLight with a remote web service call. If you look at the following integration test in the StatLight source http://github.com/staxmanade/StatLight/blob/master/default.ps1#L687 This
demonstrates spinning up a CassiniDev instance to host the remote web service. Start StatLight with the port of that instance. And stopping cassiniDev when the test is complete.
You can then look at the following to find out how to call the remote service (based on the given querystring metadata passed in from statlight) http://github.com/staxmanade/StatLight/blob/master/src/StatLight.RemoteIntegration/StatLight.ExternalWebTest/Tests.cs#L46
You can't get this functionality in the v1.1 version. Go download the v1.2 version (which is still in the "Planning"
stage) on codeplex).
When I get around to it - I will try to post a wiki article in the documentation area of this project site explaining in detail these steps.
Hope this helps.