I tryed to instanciate Excel from my C# Code

xlApp = new Microsoft.Office.Interop.Excel.ApplicationClass();
xlWBook = xlApp.Workbooks.Add(MyNull);

The second line runs on an error: "Old format or unvaild type library. (Exception of HRESULT: 0x80028018 (TYPE_E_INVDATAREAD))".

On the machine there is exclusively Office 2007 installed. No other version was ever installed. Consequently the reference I added was to the installed Microsoft Excel 12.0 Object Library file and I get the reference to "Microsoft.Office.Core" and "Microsoft.Office.Interop.Excel". My colleges who created the same program with the same code can run it without error on their machines.

Who has help?
Patrick