I could reproduce it, but just once, and just after changing the interface view from Classic Interface to GTK and back again.
In my case it was the equalizer, which stayed on screen...
Now (after repeating those steps) I am not able to reproduce it anymore.
There are many changes in trunk, which have not yet been released in Ubuntu, which might be the reason for my experience.
@Jarosław Guza: AFAIK a new version of Compiz will be released to Ubuntu 13.04 soon, please retry with this one then and post your experience here. Thanks.
I could reproduce it, but just once, and just after changing the interface view from Classic Interface to GTK and back again.
In my case it was the equalizer, which stayed on screen...
Now (after repeating those steps) I am not able to reproduce it anymore.
There are many changes in trunk, which have not yet been released in Ubuntu, which might be the reason for my experience.
@Jarosław Guza: AFAIK a new version of Compiz will be released to Ubuntu 13.04 soon, please retry with this one then and post your experience here. Thanks.