There are circumstances where, after minimizing a project to the Dock, where the Playhead will remain visible even if the window is in the Dock. This only happens if you save a layout with the Project window minimized, so the solution is to not save a layout with the Project window minimized.
Playing a Soundtrack Pro movie using Digital Cinema Desktop with preview set to Fulls screen will stop updating about 10 seconds after scrubbing the playhead.
The solution is to open the Utility window and click the Video tab so a small version of the movie appears on the main display. Digital Cinema Desktop will now work as expected when scrubbing.