After apt-get dist-upgrade I got this "Could not initialize the browser's security component. The most likely cause is problems with files in your browser's profile directory. Please check that this directory has no read/write restrictions and your hard disk is not full or close to full. It is recommended that you exit the browser and fix the problem. If you continue to use this browser session, you might see incorrect browser behavior when accessing security features."
I tried many possible solutions discovered in internet, but the only thing helped was removing of secmod.db file from my profile directory of firefox. I have no idea what this file is for, but it works. If you are having the same problem, backup your ~/.mozilla directory first before trying this or other solution which involves removing of files.