Only a few songs crash after tuning

New to downloading cdlc's. For the most part at least 9 out of 10 songs work. I have a mac and have the new mono toolkit with the song creator that converts p_psrac to m_psrac and that works fine. BUT a few songs seem fine all the way to tuning and when the song should play after tuning the screen freezes and i have to restart rocksmith through steam. I just tried with sasp download of the verve lucky man and it freezes. Any idea why? Same thing with hand that feeds, nine inch nails...don felder, heavy metal..... lover boy, turn me loose. sucks because i was so looking forward to playing them!