Using Unity 12.04 I have a black bar, a few pixels wide, appearing below the panel. This over-writes the top of a window which is immediately below the panel.
Although this may seem a minor problem it is irritating as the bar flashes as it builds up over time and this is extremely irritating. It also doesn't fit the theme (Ambience) and looks bad.
If I reveal the launcher and then hide it again, the part of the line covered by the launcher disappears, but it will re-appear again slowly over the new few seconds.
This seems to apply to other interface functions such as a mouse click or the appearance of a tool-tip, though in those cases it affects the whole bar.
Is there any way of removing this behaviour ?.