Steps to reproduce:

1. Compile and run the attached test
2. Press the button in the frame "frame1"
3. Observe a modal dialog is shown
4. Wait for several seconds until the dialog is disposed
5. Wait for another several seconds until "frame2" is shown

Expected behavior: "frame2" is an active window
Actual behavior: "frame2" is in the background

Indeed, at the moment when frame2 is shown the modal dialog has been already disposed, so it must not prevent frame2 from being activated on show. I have also noticed, that frame2 is really activated, but immediately after this frame1 is activated again.