CRecordSet ReadOnly in C++ Dll called from .NET

We are moving our existing VC++ V6 app to .NET using Visual Studio 2005 beta. To save on time we have been able to wrap up a lot of our existing base code into a separate C++ project within the .NET application. The main .NET application uses ADO.NET to connect to our SQL Server DB, the old C++ code uses ODBC via classes derived from the MFC classes, CDatabase and CRecordSet.

We have completed some initial coding of the application and have been able to execute our old C++ dialogs from within the .NET application and can view the correct data in them (returned via CDatabase/CRecordset). However, we have been unable to update any data using the old C++ based dialogs using the classes derived from CRecordSet, the CRecordset derived class we have always returns an exception reporting that the recordset is readonly. This occurs when Edit() is called on our class. Note that this code is proven under our existing VC++ V6 application which can access and update the same table in the same database on the same server with no problems.

I have ensured that there is a primary key on the table, that all permissions are correct and that the CDatabase and CRecordset objects are not being created in readonly mode. Any ideas as to why this is happening