I have a recently set up SL 7.2 using Gnome. Something very strange
happened while trying to use the mouse and now only root can log in
and get a sensible screen. All other users, including newly-created ones,
just get a dark screen and a restart. Here's the output from abrt-cli.

id d58baaa96d91911e676a06016b2268842404bb1f
reason:         gnome-shell killed by SIGSEGV
time:           Tue 11 Oct 2016 16:25:28 BST
cmdline:        /usr/bin/gnome-shell
package:        gnome-shell-3.14.4-37.el7
uid:            191 (mm)
count:          1
Directory:      /var/spool/abrt/ccpp-2016-10-11-16:25:28-27878

id 31c6e963eb58a065c6f0bd5026c8bcae29cc71cb
reason:         gnome-clocks killed by SIGSEGV
time:           Tue 11 Oct 2016 16:20:23 BST
cmdline:        /usr/bin/gnome-clocks --gapplication-service
package:        gnome-clocks-3.14.1-1.el7
uid:            191 (mm)
count:          1
Directory:      /var/spool/abrt/ccpp-2016-10-11-16:20:23-15321

Please tell me how to fix this problem!
 Malcolm