Version 4.2 adds a new "More" button to the songs list to save space in the list. However, this button causes a crash if any of your songs have incomplete links to recordings. You can temporarily work around this by turning off Settings > Appearance > Song Buttons In Narrow Lists > More. It will be fixed in version 4.2.1.
I've submitted this fix and it should be available in 2-10 days, depending on Apple's turnaround time.
Set List Maker 4.2.1 and BandHelper 2.4.1 are now available for download. That should fix this problem.