I have so far upgraded three Ubuntu 16.04 laptops to 16.10. Two of them were personal machines, and one a work machine which I upgraded at home over the weekend. In all three cases, the upgrade itself went smoothly (as I have come to expect of Ubuntu upgrades) with the only artifact being on my work laptop where 16.10 rendered the fonts bigger, which I addressed by backing the sizes down.
At work, machines get to the outside world via a proxy server that requires authentication, which I implement on my laptop in two ways: cntlm for desktop use, and with /etc/apt/apt.conf for apt (they use different accounts). Neither worked. A browser configured to use cntlm reported that cntlm could not reach the proxy server, and apt reported that it could not resolve the name of the proxy server. However, nslookup of the proxy server name reported its IP address.
After booting the laptop into the 16.04 partition, both ways of going through the proxy server work perfectly, with no configuration change. [As I have described in another thread, any machine I setup has two bootable partitions, and when I upgrade, I leave the original root partition untouched so I can go back and forth as needed.]
I am at a loss as to where to begin troubleshooting. It's as if something in 16.10 is preventing processes from using a proxy service, but that makes no sense: firstly why would it do that, and secondly, how could it do it?
Googling does not find anything relevant. Thanks in advance for any suggestions.