Ubuntu 12.04 suddenly feeling more like an Alpha

[Colin Law]

12.04 Alpha has (for me) been amazingly stable right since Alpha 1
release.  Till today.
Has anyone else running 12.04 Alpha found that it has suddenly gone
awry with a round of updates?  It starts ok but then the GUI just
seems to grind to a halt.  The clock in the top panel stops and
nothing much works.  I have to resort dropping back to a terminal and
restarting.  Strangely I can't find anything in the logs to indicate
what the problem is to see if there is a relevant bug report.  I tried
the previous kernel but no different.
I am not complaining as it is an Alpha after all.
Hopefully it will all start working again with some more updates.

Colin