.Net Open Client error - Could not load file or assembly 

My platform is as follows:

Progress code compilation done in 10.2B (64bit)

OpenEdge 11.6 (64 bit) running on Windows server 2012 R2

For ProxyGen, compiler command:  C:\Windows\Microsoft.NET\Framework\v4.0.30319\csc

For ProxyGen, XSD Generator: C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Bin\x64\xsd

Proxy files are generated successfully (AppObject.dll, Progress.Messages.dll, Progress.o4glrt.dll).

When I debug the web service on IIS Express in Visual Studio, I get the following error: 

"Could not load file or assembly 'Progress.ssl' or one of its dependencies. An attempt was made to load a program with an incorrect format.".

What am I doing wrong here?