I encountered an odd issue today.
I received an Internal Server Error for a .NET 4 application:
Calling LoadLibraryEx on ISAPI filter "C:\Windows\Microsoft.NET\Framework\v4.0.30319\\aspnet_filter.dll" failed
I looked around for a quick solution and found a few articles which suggested running aspnet_regiis -r from the Framework64 directory. This didn’t work.
Then, I noticed the path separator is doubled in the message. Removing this extra backslash fixes the issue.
To Fix in IIS 7:
- Hit WINDOWS KEY + R, and run inetmgr
- Highlight either your machine or site node in the left panel
- Choose ISAPI Filters from the middle panel
- Expand the ‘Executable’ column in the ISAPI Filters view
- Double-click the offending filter (in my case, ASP.NET_4.0.30319.0)
- Remove the duplicate ‘’ and click ‘OK’
- Restart the service and everything should be good