If You start Select Radius function and than start Measure (of course doing Clear Selection after selection) the Select Radius function is not closed (similar like Measure function before Start and Stop button wasn’t available). We can see small radius circle of selection on every Measure vertex. Please see the attached movie.
Similar situation is happens using Select Polygon. When You Clear Selection, selection is still active. Selection function cannot be closed by Esc either. So when You want to do measurement after selection You have two function in one: Selection and Measurement . Of course Measurements can be stopped by Stop button or Esc.
(MG 2.5 RC2 Apache without any changes, Windows 7, Server 2k8r2)