After AutoIt the handling of COM errors has been "fixed". Now nested COM operations crash the script in case of an error even when there is a COM error handler. Edit: All 3 problems have been fixed in AutoIt Here you find a fixed version of function _Excel_RangeFind. I simply removed all nestings and added the missing COM error hander:   Another function that needed some modification is _Excel_BookOpen. It crashed when a workbook was opened using _Excel