Calling LoadLibraryEx on ISAPI filter failed (v4.0.30319)

I installed .Net 1.1 on a Windows Server 2008 (which already had .NET 4 installed). Afterwards, I started getting the following error:

HTTP Error 500.0 - Internal Server Error Calling LoadLibraryEx on ISAPI filter
"C:\Windows\Microsoft.NET\Framework\v4.0.30319\\aspnet_filter.dll" failed 

I have tried running aspnet_regiis without success. I have also tried the suggestions by Rick Strahl but to no avail.

I have also removed .NET 4.0.30319 using the cleanup tool. When I reinstalled it, The error was still there. I have already removed 1.1 but still i get that error. Please help.

Solution 1:

From error one can observe that path mentioned was incorrect(Extra slash before .dll file). Edit ISAPI filter and edit the path to remove extra slash.

Solution 2:

Resolved by adding a new asp.net site and assigning a new application pool.

Solution 3:

This fixed the issue for me as re-creating the website didn't work:

http://www.west-wind.com/weblog/posts/2011/Apr/04/Error-on-64-Bit-Install-of-IIS-LoadLibraryEx-failed-on-aspnetfilterdll

This is worth reading, as long as the link lives, but in summary, there are 2 fixes

1. (quick fix) Set the app pool's Enable 32-Bit Applications to true
2. (ideal fix) Adjust the system.webServer/isapiFilters configuration setting so that IIS will use the correct dll when operating in 64-bit mode