Hi there, I read some topics about how some people is unable to transfer some mp3 files to their devices. Well, it happened to me as well. However, I found out a way (kinda extreme though). I don't know if this issue has been solved already, but here it goes anyway: I have Cool Edit pro installed on my laptop, so if there is any mp3 file that SS2 doesn't recognize then I open that file with CoolEdit and save it again at the same bit rate. Now, I "re-import" the file to the SS2 library and LISTO! you can transfer it.
p.d. I haven't proved with MMJ or another mp3 converter