[TYPO3-windows] Typo3 Backend 500 Server Error After Upgrading to T3 4.3.1 on Windows 2008 IIS7

[Shade]

*Problem:  Cannot login to typo3 backend after upgrade, page giving 500
Internal Server Error.*

We recently moved our Typo3 site (4.2.x) from a Windows 2003/IIS6 server to
a new host which had Windows 2008 and IIS7, and after a few initial hiccups
during the migration, we eventually got the site running on php 5.3.x and
upgraded Typo3 to 4.3.0.

Unlike previous versions of Windows 2003, you do not need to download the
'junction' tool to create the alternative symlinks, because Win2k8 has built
in use of 'mklink' command that serves the same purpose.

However, recently we tried to upgrade from 4.3.0 to 4.3.1 by deleting the
typo3_src junction folder and then creating it again pointing it this time
to typo3_src-4.3.1 folder, which is how we normally upgraded previous
versions on the old windows server.  Unfortunately, this blocked us out from
accessing the Typo3 backend.  The front end site still loads fine, the
backend login page loads fine, and so does the install tool.  However, after
entering the username/password to enter the backend, the login page
redirects to  backend.php but gives the 500 server error.

We have tried deleting all the junctions and creating them again from
scratch, but still the same problem.  We even created the junctions to
revert back to 4.3.0 and still getting the server 500 error, which suggests
the problem is not with Typo3 source files, but a configuration issue
between Windows 2008 / IIS7 / Typo3.

Typo3 install tool reports that writeable folders are indeed writeable, and
considering we already recreated all junction directories, which is almost
like installing typo3 fresh, then what can we try next to resolve this
backend.php error?


- Junaid


Full Error Details
###############


HTTP Error 500.0 - Internal Server Error The page cannot be displayed
because an internal server error has occurred.
 Detailed Error Information
  Module FastCgiModule Notification ExecuteRequestHandler Handler
PHP_via_FastCGI Error Code 0x00000000
  Requested URL http://www.example.com/typo3/backend.php Physical Path
C:\inetpub\wwwroot\typo3\backend.php Logon Method Anonymous Logon User
Anonymous
 Most likely causes:

   - IIS received the request; however, an internal error occurred during
   the processing of the request. The root cause of this error depends on which
   module handles the request and what was happening in the worker process when
   this error occurred.
   - IIS was not able to access the web.config file for the Web site or
   application. This can occur if the NTFS permissions are set incorrectly.
   - IIS was not able to process configuration for the Web site or
   application.
   - The authenticated user does not have permission to use this DLL.
   - The request is mapped to a managed handler but the .NET Extensibility
   Feature is not installed.

 Things you can try:

   - Ensure that the NTFS permissions for the web.config file are correct
   and allow access to the Web server's machine account.
   - Check the event logs to see if any additional information was logged.
   - Verify the permissions for the DLL.
   - Install the .NET Extensibility feature if the request is mapped to a
   managed handler.
   - Create a tracing rule to track failed requests for this HTTP status
   code. For more information about creating a tracing rule for failed
   requests, click here <http://go.microsoft.com/fwlink/?LinkID=66439>.