I found it the problem. Thanks to the replies of James and Rusell I came to the conclusion that the problem was not in my program. Because I create the context menu on the fly in my program itself, and don't register a dll it could not be this. So I came to the bright idea to uninstall Zipgenius, which had caused me problems before, and voila, problem has gone. Zipgenius registers a contextmenu for zipfiles. Either due to a bug or an incompability due to the fact that zipgenius dumps its version 1.60 dll's in the system directory, which I replaced by version 1.70, it was the zipgenius contextmenu handler that raises the exception, which obviously only appears within the Delphi IDE. Gerard PS. No offence Matteo Riso, but you should maybe look into this.