Unity window focus.

[MS]

I am finding it intensely annoying that if I move the mouse quickly, 
often when making for the X in the left hand corner, I loose focus on 
the application window in question and am left with a display of all 
windows/workspaces.  I then have to right click on the chosen window to 
reselect it before gingerly moving the mouse to close it.

This is with U 12.04 and I expect more recent versions of Unity have had 
these rough edged smoothed out, I am just not a cutting edge person.

Is there a simple fix?

Many thanks

MS