package ca-certificates 20160104ubuntu1 failed to install/upgrade: triggers looping, abandoned

[Shmulik Anglister]

I tried to upgrade to 16.04 from 14.04, following a system prompt.
First I got a "third party sources disabled" error. It said "some third party entries in your sources.list were disabled." I closed the dialog box and upgrade resumed.
Then after a while I got a "could not install the upgrades" error dialog box. It said "the upgrade has aborted. Your system could be in an unstable state. A recovery will run now (dpkg-configure-a)".
Well, the upgrade may have been aborted but my machine is running 16.04 now.
It is somewhat unstable as I get these error messages on reboot and some features of the system are not available and some are not responding.
I can add that I am a low level Linux user. Ever since I installed 14.04 a few years ago I haven't tweaked it or touched in any way, except for installing updates.
Thanks,
Shmulik

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: ca-certificates 20160104ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-36.55-generic 4.4.16
Uname: Linux 4.4.0-36-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
Date: Sun Sep 4 02:04:09 2016
ErrorMessage: triggers looping, abandoned
InstallationDate: Installed on 2015-05-07 (486 days ago)
InstallationMedia: Ubuntu 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1)
PackageArchitecture: all
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.1
 apt 1.2.12~ubuntu16.04.1
SourcePackage: ca-certificates
Title: package ca-certificates 20160104ubuntu1 failed to install/upgrade: triggers looping, abandoned
UpgradeStatus: Upgraded to xenial on 2016-09-04 (0 days ago)