This must surely be a disconnect between what you're looking at and what you're hearing.
In Staff View & Event List View - make sure you have the correct track visible - i.e. the MIDI track.
Check the PRV to see what's going on, again, make sure you view the MIDI track
What can you see in Track View? If you solo the violin track, does it still play?
If you mute it does it go away?
What synth are you using to generate your note data?