I have the EXACT same issue with, only I'm Cubase 7.5. I don' t think it's a cubase issue, it's a spark VST issue with cubase. I have never resolved it, I just don't use multiple outs. Boooo. I'm win 7 64 bit.
I run this same setup, mobile but on an OLD ass macbook. I have no issue with multiple outs on cubase for mac with spark. Interesting.