interesting footnote. the problem stopped for me but not for any obvious reasons. I installed Reaper and rendered a short midi file in Reaper and Garage Band to see if it was system wide or just Cubase.
After doing that, I went back to Cubase and could not reproduce the freezes. This may be unrelated or perhaps that was enough to resolve an issue with CoreAudio.
RME babyface - 128 through 1024 sample buffers all had the same issue
UAD software + satellite installed