Thank you all for the responses.
Jim H, Mac says they have no built-in anti-virus and I haven't installed one either.
BartMan01, do you have 10.10.2 on a Mac Mini (although that shouldn't make a difference)?
avpman, yes I used 80-2 after deleting both 64 and original 80 download. I just repeated the process to make sure. It didn't go to trash immediately and didn't go there after restarting the Mac either. We'll see how long it lasts.
Maybe I should start a new thread on this, but it might help you guys help me troubleshoot this problem. While I was able to import a music library, when I click on About to find my renderers (Olive o4HD and Bel Canto REFStream), none of them show up. I know my network is good because I also downloaded the PC version of MC20 in my laptop and it quickly finds the Olive and some Sonos pieces, but needs 2 or 3 restarts of MC20 to find the Bel Canto. A Mac-Centric friend thinks this indicates an incomplete installation of Mac MC20.