While configuring the SharePoint 2010 for Forms Based Authentication, I encountered above error. To get the problem, I had to change “IncludeExceptionDetailInFaults” to true somewhere. But WHERE? Here is what solved my problem: Go to following path: 1. C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\WebServices\SecurityToken 2. Open Web.config there. 3. Add following in the “behaviors > serviceBehaviors > behavior” node. <serviceDebug includeExceptionDetailInFaults="true"/> Now try to login and see what error it gives, off to a next error