OK, starting the Content Server and doing the
http://192.168.100.4:8080 works.
So, I retried the wireless connection and it didn't work.
So, I tried the browser on 9090 to see if I got the same you did ... and I got a login screen for OpenEdge Management Console (OpenEdge is a software package I develop in, although I don't use the Management Console).
So, I tried starting the wireless connection on 8090 instead and with CC changed correspondingly, it now connects.
While a conflict over port use makes perfect sense and I know that OpenEdge does some default stuff during install that I pay no attention to, since it relates to functionality I never use, it has been nearly a year since the last OpenEdge install so if this was going to be a conflict, it should have been a conflict all along. There have been no changes to OpenEdge in eons and the only changes to Calibre have been the periodic updates.
We have more than one device running CC, but the other is my wife's and she works off her own copy of Calibre on her own machine. It has happened that I have connected to her copy, but 99% of the time there is no possibility since only one of us will have the wireless connection live at a time.
So, looks like the problem is solved ... and the reason clear ... but why it is a new problem is a mystery.