You should also update nspr package: $ sudo yum update nspr

After that, firefox will work.

I did that (yum update nspr) and it made no difference. I definitely have the latest versions:

Linux-mybg (15:54) > rpm -qa firefox xulrunner nspr nspr-4.9.2-1.fc16.x86_64 nspr-4.9.2-1.fc16.i686 xulrunner-16.0.1-1.fc16.x86_64 firefox-16.0.1-1.fc16.x86_64

yum -y update nspr firefox xulrunner

if that fails...

yum -y reinstall nspr firefox xulrunner

[sicinthemind@sicmind ~]$ rpm -qa nspr{-devel,} firefox xulrunner

nspr-4.9.2-1.fc16.x86_64

nspr-devel-4.9.2-1.fc16.x86_64

nspr-4.9.2-1.fc16.i686

firefox-16.0.1-1.fc16.x86_64

xulrunner-16.0.1-1.fc16.x86_64

The purpuse for the {-devel,} is to make sure to include whether or not your nspr-devel is up to date as well.