In the last few versions a shortcut conflict has crept in. The Debug command and the Debug Last Script command (button in Project Explorer toolbar) were both assigned the shortcut Shift+F9. This can cause some subtle issues as for example http://code.google.com/p/pyscripter/issues/detail?id=496. This has now been fixed in version control but in existing installations you need to manually change the Debug shortcut to F9 (or anything else you like). F9 is consistent with the PyScripter help file.