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?

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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.