Bug #786973 is possible duplicate, but it needs more details.
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> I opened Firefox's context menu and a fragment of the workspace switcher disappeared and reappeared only after I closed a Nautilus window from the window list applet on the bottom panel.
Hasn't VT switching helped?..
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Well, as it affects not only panels, but also applications, the bug description should be slightly updated.
Bug #786973 is possible duplicate, but it needs more details.
---
> I opened Firefox's context menu and a fragment of the workspace switcher disappeared and reappeared only after I closed a Nautilus window from the window list applet on the bottom panel.
Hasn't VT switching helped?..
---
Well, as it affects not only panels, but also applications, the bug description should be slightly updated.