Ajax autocomplete extender is not working in IIS 7

   I am Using Ajax autocomplete extender using web service to load details in textbox.

It is working in development PC. But When i deployed application in UAT server not working in IIS 7 Window server 2008 R2.

I check the tracer using fiddler, Getting 401 Unauthorized error. But I check the Permissions in IIS all vailable.

I am using VS 2010 and .net Frame work 4.0 and Ajax control 4.0

Any suggestions.