I just installed and updated Ubuntu Gnome 16.04 LTS on my desktop PC.
If I click on the power button (top right icon on the desktop), then I click the larger power icon, then I cancel the operation, some of the tray icons (Skype, Dropbox and OwnCloud in my setup) become transparent. They are still in the tray, but you can't see the icons.
You can check a picture:
and a video of this behaviour from this link:
Any suggestion? Is it a bug? Thank you very much for your help!