sgen.exe error in compiling C# dll

I was working with a Biztalk project that called a dll from a expression in a orchestration.
I was working in Visual Studio 2005 SP3. At this date BizTalk requires VS 2005

I go the error sgen.exe.

I found that if I compiled the project in RELEASE I get this error. If I compile in DEBUG I do not.

I do not know if this will effect the speed of the C# process. This step was very small and I was not concerned.

Microsoft called me back and had me go into the properties for this project. On the build tab. I changed the generate sirialzation assembly from AUTO to OFF. This let me compile(Build) in RELEASE mode.