Expression Encoder 4 assembly within ASP.NET, IIS7.5 and VS2010

Question

Hello Stack Overflow Community,

We have a problem whilst trying to implement an expression encoder assembly into our project and running it through IIS 7.5.

We are using VS2010 and .NET4. We have ensured the project is targetting x86 cpu type and when running our application within the VS development server everything is fine.

When we deploy the application through IIS 7.5 (/localhost) a configuration error is thrown:

<add assemby="Microsoft.Expression.Encoder, 
 Version=4.0.0.0. Culture=neutral,  
 PublicKeyToken=31BF3856AD364E35" />

We have trawled the internet for answers but have not found an answer..

Any help appreciated.