XL(Ez)Automation and Excel 2013

I have a C++ app that communicates with Excel using XL(Ez)Automation sample code as a starting point. My app has worked with Excel 2003 through 2010. Excel 2013 has broken it. I get three popup dialogs which say something like "can't find Microsoft.xlsx", "can't find Office.xlsx", and "can't find EXCEL.EXE". The interesting thing is that once I dismiss the sequence of error dialog boxes, the spread sheet I created does in fact show up properly in Excel 2013 and seems correct. Only Excel was installed, not the entire office suite. I tried reinstalling Excel, but Microsoft now ties not only the activation code but the user account to the software, and since another engineer installed it, I can't download the software again without using his account, and of course today he is on the road. I searched online and my PC for Microsoft.xlsx, and Office.xlsx and didn't find them. I don't remember the "EXCEL.EXE" path from the error message, but it was something like "\15\Root\Office15\Excel\EXCEL.EXE. I think the Excel path is obtained by an XL(Ez)Automation call to windows. It is not hard coded in the C++.

Is anyone else using XL(Ez)Automation with Excel 2013 and experiencing this series of errors and figured out how to fix them? I'd obviously love to fix it without editing the C++ code which is in use and would require extensive testing for recertification by my client.

Thanks for any help