There is a problem running .NET applications that use COM interop on 64 bit windows. .NET applications are typically built so that the JIT compiler will produce code for the runtime platform. So on Windows 64 we get a 64 bit application when it is running. However, chances are all your COM classes are 32 bit dlls. OOps. These will refuse to load into the 64 bit process.
Fortunately there is a solution. One is to compile the thing and set the build option to fix the processor type in the application project properties. However, if you only have the built assembly you can use the CorFlags utility to change the execution environment for the assembly. CorFlags assembly.exe /32BIT+ will force the application to run as a 32 bit process. If the assembly is signed you may have to add the /Force flag which will break the strong name signature but when I did this to the IronPython console executable it seemed to work ok.