It was installed under SP2, so I have no basis for comparison.
I also do not run the MS firewall as I’m behind a router, but that shouldn’t be an issue since zBrush shouldn’t be calling home anyway, right? Certainly not 5 or 10 minutes into a session.
The freezes are very sporadic and so far have only occured during zSphere Modeling, never during mesh painting or manipulation (at least, not yet). The freeze has ALWAYS occured within a few minutes of using zSpheres (when I say sporadic, I mean I don’t know how long it takes before it actually happens, but it always happens…It is completely reproducible if you play with zSpheres long enough.). I haven’t gotten far enough along yet to use other features, like creating textures, so there could still be more surprises waiting for me.