I ran into this error on a new project:  Handler “PageHandlerFactory-Integrated” has a bad module “ManagedPipelineHandler” in its module list.

A web search showed this was due to asp.net not being fully installed on my 2008 R2 server.  So, I installed it using the following command:

%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe -i

The same command on 32-bit windows would be:

%windir%\Microsoft.NET\Framework\v4.0.21006\aspnet_regiis.exe -i