Looks like its not the firefox update at fault but the new kernel, which was also released about the same time, not playing nicely with our NFS file servers. Hopefully this can be resolved soon, currently am having users boot into the previous kernel version (2.6.32-573.26.1.el6.x86_64 as opposed to 2.6.32-642.el6.x86_64).
Sorry for the, somewhat, false alarm about firefox. Jesse
