Thanks. Tracked at:
http://www.ventismedia.com/mantis/view.php?id=5754

-Rusty

1 On floating Now Playing window, click a track
2 On Windows task bar, clik on another app button
3 On Windows task bar, clik on MM app button

Expected: focus still in Now Playing
Observed: focus lost from Now Playing

Note: Other floating windows e.g. Equalizer, Track Properties behave as Expected.