[xubuntu] Help troubleshooting upgrade to 16.04

Hello,

I've just upgraded from Wily (15.10, I think) to 16.04, via 'do-release-upgrade' in a terminal.

16.04 now appears in GRUB, but when I select it I get first the xubuntu login screen, then a black screen with a few lines of code, ending with a couple of lines to the effect of 'starting manager UID 116' then 'stopping manager UID 116' or something close--foolish of me not to have written them down, can do and come back if necessary.

I'm now working from a 16.04 live CD to try to troubleshoot the problem.

Any suggestions would be greatly appreciated.

Thanks in advance.