More info that may be helpful. On my system the steps do not result in a crash. However, the second undo does not remove the inserted track, and closing Sonar results in sonarpdr.exe still being active in the Task Manager processes tab. After ending this process, opening Sonar again results in a loud continuous noise in my system. It goes away if I close Sonar, then stars again when I reopen. It won't go away until I restart my sound card. I have never seen the behavior before trying the specific steps outlined above.
Clearly something fundamentally screwed up here.