This error occurs when midi music could not be successfully outputted. Make sure your midi output device ingame is 'Microsoft MIDI Mapper'. Refer to No music fix.
Close all background running applications. Overseer seems to be sensitive to certain programs running at the same time.
This happens when the game is minimized, so don't do it. If this occurs you will need to restart the game and/or find the cause of the minimization, see Game minimizes itself
The game might not play back any videos for you and instead great you with an error regarding your MPEG-2 configuration. In order to resolve this:
regsvr32 /u ffdshow.ax