Ubuntu :: Toolbar - Some Icons Are Not Clickable With The Left Mouse Button

In my desktop toolbar on the right side where my running applications are shown etc. I have some problems:

1) After a while and after some messages have been shown and applications started, there is a growing gap which gets larger. When I move the mouse over the gap, I see tooltips belonging to the application to the right which is always a different one so I assume that it is a toolbar problem and no application problem.

2) Some icons are not clickable with the left mouse button, e.g. Rhythmbox. When I left click on it, nothing happens.

3) When I open the volume control with a left click, I cannot close it by clicking somewhere else. I always have to click on the "Mixer" Button to see a whole window and then I can close it.