I have a situation where I'm using clientside ASP.NET AJAX requests to a WebService in the same web site. The WebService folder is protected by FormsAuthentication. It seems to work fine, execpt when I load test the website using VS2008 Test Edition, a majority of the web service calls are generating HTTP 401 responses.  Any ideas what I can look at?

Thanks! 

Do your tests perform authorization before trying to access the service? A 401 is an error code denoting  unauthorized access:

Make sure that authorization is performed by the tests, or disable forms authentication during testing.

Yes, my tests are doing authorization. The tests work fine when running them with a single user. It's only when I put the sure under a load that these 401 errors start popping up. When they do happen, it's not for every test. 

To solve this issue, I removed the WebService directory from FormsAuthentication using the <location> tag in the web.config. I then rewrote the WebService to do it's own user verification in code.