Open the settings dialog on one Virtual Desktop (Menu->Click settings without going to the submenu) , then move to another Virtual Desktop or screen and try and open the settings dialog again (Menu->Click settings without going to the submenu), Notice you get settings show up in "Tasks" but clicking on them does nothing, To resolve you have to go back and find the old settings window and close it first. This can be an issue if you miss configure screens and that dialog is now on a screen that doesn't show anymore.
(Tasks is only configured to show windows on this Virtual Desktop)
An unrelated second time I got this but I couldn't reproduce it
- Simotek clicks settings in tasks
- Simotek clicks firefox
<Simotek> Random settings dialog comes up
- Simotek closes dialog
- Simotek repeats for another settings dialog