To enable your COBOL programs to interface with languages such as C#, the .NET Framework requires that any variables passed to the framework from the COBOL program are marshalled. From extend version 9 onwards, marshalling and .NET support is handled internally. However, if you experience problems with this, you may revert to the previous method of using the AcuToNet.dll interface by following these steps from a command prompt:
regasm20acu /register /codebase AcuToNet.dll
regasm40acu /register /codebase AcuToNet.dll
marshal.exe /RegServer