I have the same problem like in this topic:
http://social.technet.microsoft.com/Forums/da-DK/exchangesvrtransport/thread/686d1a90-a016-4a4c-ae2e-6725914a5d5a?prof=required
The latest Windows/Exchange 2010 Updates are installed.
The solution from fiona didn´t help:
"I would suggest you perform the following steps to troubleshoot this issue:
- Remove the exppw.dll entry from applicationhost.cofig (c:\windows\system32\inetsrv\config)Note: Remember take a backup before you remove the line.
- Then registered the exppw.dll by following the below steps:
- IIS Manager -> Select the Server Name in the left Pane -> Open Modules in the middle pane.
- Click on ‘Configure Native Modules’ in the right pane -> Click the button ‘Register’ -> Type the name as ‘exppw’
- Browse and select the path of above file as: c:\Programme Files\Microsoft\Exchange Server\V14\Client Access\OWA\Auth\exppw.dll.
- Made sure that the 'exppw.dll' is only present at OWA level and not at any of the top heirarchy.
- Then ensured for this module in OWA (VDir), ‘Module Type’ is set to ‘Native’ and ‘Entry Type’ is ‘Local’
- Run IISreset /noforce
Let me know if this works. Thanks. "