HTTP Error 500.21, "bad module "ManagedPipelineHandler" in its module list"

This is often caused because the .NET 4.0 framework is not registered properly.  Even though it may be installed - there have been reports that the registration process often needs to be done again.  So if you get the following error:

HTTP Error 500.21 - Internal Server Error
 
Handler "WebServiceHandlerFactory-Integrated" has a bad module "ManagedPipelineHandler" in its module list

To resolve the issue register the .NET 4.0 Framwork by doing the following:
1.  Right-click on a Command Prompt and select Run as Administrator (Windows 7).
2.  At the command prompt type:
   %windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_regiis.exe -i
3.  Hit enter.
4.  Close the command prompt.