Hi Patrick,

I came across a similar issue when Excel popped up a dialog on startup (activation, end of trial period, ...).
Could this cause the problem?

Just another guess:
Are the VSTO (Office 2007) installed (correctly)?

HTH

>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