By default, the standard web interface includes a line in the web.config that will redirect users to a splash page saying an error had been reached and to contact support. Unfortunately, this does not help us in troubleshooting. You can however edit this piece in the web.config:

     <!--

      The <customErrors> section enables configuration 

      of what to do if/when an unhandled error occurs 

      during the execution of a request. Specifically, 

      it enables developers to configure html error pages 

      to be displayed in place of an error stack trace.

    -->

    <customErrors mode="RemoteOnly" defaultRedirect="Error.htm">

    </customErrors>

To become:

     <!--

      The <customErrors> section enables configuration 

      of what to do if/when an unhandled error occurs 

      during the execution of a request. Specifically, 

      it enables developers to configure html error pages 

      to be displayed in place of an error stack trace.

    -->

    <customErrors mode="Off">

    </customErrors>

Now, this will show the raw error and help with troubleshooting situations.