I resolved this issue by removing ~/.mozilla/firefox/*/XUL.mfasl and restarting Firefox, following the instructions from ubuntu forums (http://ubuntuforums.org/showthread.php?t=624732).
I resolved this issue by removing ~/.mozilla/ firefox/ */XUL.mfasl and restarting Firefox, following the instructions from ubuntu forums (http:// ubuntuforums. org/showthread. php?t=624732).