Comment 3 for bug 1617020

I too was affected by this bug.

Running 14.04.5 (ASUS NX500J Notebook), no outstanding updates - but HWE upgrade performed to 16.04 compatible as prompted before upgrade, upgrade from terminal to 16.04.1:

$ sudo do-release-upgrade

Failed as described by Boki during initial upgrade.

Upon reboot I was unable to login via the UI, the UI looked messed up and was unresponsive.
But I could access the terminal via: ctrl+alt+f1

I was able to restore a seemingly working 16.04.1 using the following steps:

$ sudo apt-get dist-upgrade
This showed that I was missing a couple of dependencies, the names escape me - but it wasn't the offending package.

$ sudo apt-get -f install
Installed missing dependencies.

$ sudo apt-get dist-upgrade
This showed a large number of unneeded packages and more importantly a even larger number of up-gradable packages
I installed them, while being randomly being prompted for the password for the encrypted swap-partition.
It took a while but it succeeded.