Super Perfundo On The Early Eve Of Your Day

I run an M Audio Fast Track Pro Interface and run all sound through that. I am working on a song right now where that every time it gets to a certain parts where horns and strings are added, it starts cracking and its all jumpy and the sound doesnt sound that great. 

WHAT DO I DO!?

I have the Eq on and the low&high freq’s turned down. suggestions!?