Severe intermittent hanging with Firefox, F16, KDE ?

[linux guy]

Firefox is intermittently freezing from time to time in my KDE
sessions, hanging my whole machine for 20 seconds to a minute every 20
minutes or so.

Anyone else having this problem ?

$ yum list firefox
firefox.i686                                      9.0.1-1.fc16

$ uname -a
Linux server.localdomain 3.1.6-1.fc16.i686 #1 SMP Wed Dec 21 23:18:01
UTC 2011 i686 i686 i386 GNU/Linux

$ yum list kdebase
kdebase.i686                                     6:4.7.4-2.fc16
                             @updates

Thanks