HTTP Error 500.0 – Internal Server Error
Calling LoadLibraryEx on ISAPI filter “C:\Program Files\Microsoft Dynamics CRM Server\Server\bin\DefaultAddonFilter.dll” failed.

The CRM application server was hosted on a 64-bit server with 8GB memory, running Windows Server 2008 R2, IIS7.

The cause of this problem was related to missing Microsoft Visual C++ 2008 SP1 runtime components.  After installing these component, CRM worked like a charm.

Below are links to the runtime libraries in case others run into this issue:

x64: http://www.microsoft.com/downloads/en/details.aspx?familyid=ba9257ca-337f-4b40-8c14-157cfdffee4e&displaylang=en
x86: http://www.microsoft.com/downloads/en/details.aspx?familyid=a5c84275-3b97-4ab7-a40d-3802b2af5fc2&displaylang=en