createsend-dotnet.dll has mismatched identity 'cs'

Hi,
I just downloaded and installed the .NET API.  I am working in WinForms VS 2010 with the .NET Framework 4.0.  I installed the 'createsend-dotnet.dll' and ran into the following error on runtim:

Could not load file or assembly 'cs, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.   

The createsend-dotnet.dll properties has all the correct information the error message says it needs.

Any ideas?

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