fix a broken gnome desktop ?

[Mike Wright]

Hi all,

Following a recent kernel update I rebooted and can no longer use 
Gnome3.  I receive this error:

     "Oh no!  Something has gone wrong.  A problem has occurred and the 
system can't recover.  All extensions have been disabled as a precaution."

Usually there is no mouse after this happens.  A "return" returns me to 
the login screen and I can choose one of the different desktops from 
there, all of which work.

I am loathe to yum remove, yum install.  The remove wants to take 554MB 
of packages with it and I'm not willing to gamble that I'll have a 
usable system afterwards.

Anybody seen this before?  How did you recover from it?

Thanks for your help,
Mike Wright