Wish I had an answer for you, but unfortunately, I have almost exactly the same problem except UC 1.7.0 loads and connects, but won't work with QMix (my iPhone sees the mixer but the mixer does not see my iPhone). Tried a 4 hour Windows 7 upgrade (thought maybe I needed the platform update, tried loading 1.7.5.5, but nothing. My message reads something like "did not load properly, try rebooting or reloading the software".
Frustrating!