14.04 after upgrade freezes with fire fox

[Linda]

I upgraded from 12.04 LTS to  14.04 LTS I run this machine with gnome flashblack (Metacity)
when I run firefox it freezes the machine so you have to turn it off and restart. It ignores the keyboard and you can not even ssh in and kill the processes. I tried running it in a terminal and I get the following error
GLib-CRITICAL  g-slice-set-config:assertion 'sys-page-siace == 0' failed
Any ideas on what might be missing or need to be fixed.
           Linda