Resolution: after a lot of back & forth by email & skype, we found two things:
1) The calibre installation was somehow corrupted. Fixed by uninstalling calibre, deleting the calibre folders, and reinstalling. At this point the content server test worked.
2) Turned off McAfee. CC could connect. After fighting a bit we found that the local network was marked as "untrusted" in McAfee. Changed it to trusted and CC could connect via both wireless device and content server.
Thank you, LadyLori, for your patience. As you said, we both learned something.
