New Firefox Won't run

[Don Vogt]

Yesterday I updated to kernel 2.6.32.9.70 fc12 and to firefox-3.5.9-1.fc12 and now firefox won't start. I get a notice in the bottom bar for a few seconds and then it goes blank.
I tried starting firefox in a terminal and it returned "can't load XPCOM"
I tried 'locate XPCOM' and it returned some files in /usr/lib/VirtualBox and /usr/lib/xulrunner-1.9.1/modules/XPCOMUtils.jsm

I have VirtualBox installed, but I am not trying to run firefox in virtualBox, but on the desktop.
 I just found that xulrunner-1.9.1.9-1.fc12 was installed at the same time as the new firefox so I suspect the problem is between firefox and xulrunner.
 I don't know what to try next. I have been using fc12 for a long time successfully for quite a while Any help or advice would be appreciated.