Updating Ubuntu

Earlier in the week I got around to updating the desktop to the new release of (K)Ubuntu 14.04 - I run the version using the KDE desktop - though I have lots of the ordinary Ubuntu packages installed too. Around 50 mins from the projected end of update the machine locked up - I was doing various other things at the time on it which may have contributed to this. No response to anything from mouse/keyboard - the sysrq magic keys had no effect either, but I was running an ssh server on the dekstop so I logged in remotely and rebooted.
When it came up again the boot screen appeared to think it was running 14.04 (rather than the previous 13.10) however at the login screen neither keyboard nor mouse got any reaction (and the ssh server wasn't running the machine hadn't registered with the router). I tried re-booting a couple of times with no effect.
I then broke into GRUB (at boot - press down the shift key) and booted the minimal 13.10 install (still there!) and ran the dkpg fix option (I previously tried minimal with 14.04 which again failed) which ran to completion. A reboot then gave me a working system!
Looking at the upgrade log file the last lines of /var/log/dist-upgrade/term.log read as follows:

Setting up openssh-server (1:6.6p1-2ubuntu2) ...
Installing new version of config file /etc/init/ssh.conf ...
Installing new version of config file /etc/pam.d/sshd ...
ssh stop/waiting
ssh start/running, proce

Yes it stops there! I had it down as a problem with the NVIDIA graphics driver, this might suggest something else - I wasn't connected via ssh when I was running the upgrade so it wasn't a a case of the connection dying. Still puzzled but putting this here in case it helps anyone else.
The other problem I found (so far!) is that Ctrl-Space doesn't appear to do anything - I use this key combo a lot - in Emacs. So it was a bit painful, a websearch reveled that ibus was the problem so I ran ibus-setup and stopped that grabbing Ctrl-Space for 'next input method' and assigned it to a different key.
So far everything else appears to work...