Retrieving the COM class factory for component with CLSID {XXXX} failed due to the following error: 80040154

I am running 32 bit Windows 7 Operation System which has IIS 7.5 installed.

In Visual Studio 2010, I open my solution having the web site project hosting WCF service. I have created an application in the IIS which points to the website project. The web site's bin folder has many assemblies which I need to refer. But those assemblies also have built using .NET 4 on the same computer.

I can browse the WCF serv开发者_StackOverflowice using both HTTP & HTTPS.

However, when i access the service from the test windows application (using the proxy class of the WCF contract), I get the error in question. Everything was working without problem earlier.

Anyone can help to fix the issue?. How to investigate this issue?

Error 0x80040154 means "Class Not Registered", which usually means you're depending on a COM component that hasn't been installed properly on the machine.

Is any of those Assemblies you reference a COM Interop Assembly? If so, find out what it uses and then install the appropriate COM component.