I wrote out a song with the usual.
A basic boom tap drum beat, bass line and 3 guitar parts.
I move the drum track when everything is written and I'm ready to make the drums sound like someone is playing rather than a generic beat. I write out the drum track. BTW, it's the last track. I then clone it and archive the original. I split the drums to their individual midi tracks as I like 100% control of everything. I move all the drum parts to a folder and I usually make my drum folder the first folder.
 
I write the tracks in screenset 2.
 
After splitting the notes to their own track using a cal script, screenset 1, I move them to the drums folder. I put the archived drum track in the drums folder as well.
 
Keep in mind that on screenset 2 I had a midi track, in staff view, open and now it no longer exists. I keep forgetting to close the SV as it seems whenever I forget to close it, Sonar crashes.
 
So basically, if you have a SV open, that no longer exists on  another screenset not in use, Sonar crashes.
 
Has this happened to anyone else?

I reported a related bug some time ago that the Track Pane in the SV in one screenset drops all tracks except the one that has focus in the TV of another screenset that you switch to/from. What I see in your scenario is that the track numbers shown in the SV's Track Pane follow the change in the TV, but the corresponding notes are no longer displayed in the SV when you come back until you re-select the tracks in Pick Tracks. But I can't reproduce your crash.