<i>Locking this thread.</i><br><i>Please continue here: [[/questions/1330399]]</i><br> Possible causes are that security software if blocking access to places.sqlite in the Firefox profile folder. Did you try to close and restart Firefox or reboot the computer ? Thank you for your prompt reply. I do not have any security software that would suddenly block access and it was working fine until yesterday morning. I have closed and restarted Firefox several times and followed your advice. I have also rebooted my computer.