Sometimes the Visual Studio is not cleaning the solution correct. Can you try first to Clean up the solution, with the original ref. assemblies and after that remove them and reference the new ones.
You may also try to close the Visual Studio and open it again. Sometimes it caches the old assemblies, and since they are loaded once, it doesn't want to load them again.
Hope this will helps you.
Please let us know if you still have problems.
We will be very happy to see your feedback also.
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