kJams by Metamuse Media

Yesterday I could not exit Kjams and had to force shut down...what do you think caused that?

I have the most current update and I'm using Kjams with wtkjams app along with loading rotation manually.
While trying this out it seems that every so often the program gets hung up and won't allow me to play the next song on the rotation.
If I 'mark singer as not here' it will play the next song(s ...

I have a Mac and a PC.
Do I have to purchase kJams twice? (Once for each?)