The attached example application can be used to demonstrate the problem. When opening the other applications by clicking on the widgets, sometimes the wrong widget gets the mousePressEvent, causing wrong application to launch. If this happens, the widget that gets the event is always the one that last worked correctly. Note that this doesn't happen every time a widget is clicked, only maybe 15% of the time.

To repro:
1) Click on "notepad" -> notepad opens
2) Close notepad by clicking on "X" at top right corner of window.
3) Click on "calc" -> calc should open, but sometimes notepad opens.
4) close calculator by clicking on "X" at top right corner of window.
5) Repeat until you get wrong application to open.

Note that closing the app using the mouse seems to be a requirement. If I used alt-f4 to close the launched application, I couldn't repro the problem.