Just upgraded from 15 to 16.04. I think the upgrade was fine and then rebooted at the end of the process... that's when the trouble started.
I am being dropped into emergency mode with the message:
radeon 0000:01:00.0: VCE init error (-110).
Searching through the journal shows the same error. If I continue with defaults the splash screen shows for less than a second and I'm back to emergency mode with the aforementioned error repeated.
I am dual booting Ubuntu and Win 10 and have one of the horrible hybrid Video cards. With the previous working installation I had given up on using the radeon card and was only using the Intel graphics. This is also why I am dual booting, so I can use the Radeon Card for gaming.