Paul - are you using the Select to File activity or the Export Wizard? I was running macros in my workbook, but I was using the select to file activity, forcing it to point to the macros enabled file by typing in the "xlsm" because that type of activity would not point to macro workbooks. I changed my export to the Export Wizard, running the macros after export. My initial test file opened with no error messages about the workbook being corrupt.
Let me know if that helps. I will do further testing just to make sure this is the solution for me.