I had a problem suddenly that occurred where Kjams would no longer play any song in my library. Desperately trying to work within my limited knowledge I deleted the library re-imported, still no joy. Freaking out because I had an event later today, I emailed Dave, he replied right away today, we used Ichat, he did some troubleshooting and found the problem.
I use a MacBook Pro, when connected to my system I use a Gigaport HD USB external 8 port

sound card. What happened was that when I disconnected the laptop to clean up my library, the system defaulted to bluetooth without me knowing. This "prevented" the program from either showing graphics or playing. Something to keep in mind is to check your sound card output. A hard lesson, but easy fix. Dave saved my bacon and a few hairs on my head. Thanks for a great product.
Greg