hello, please try to [[Reset Firefox – easily fix most problems|reset firefox]] and see if this can address the issue... please run a full scan of your system with the security software already in place and different tools like the [http://www.malwarebytes.org/products/malwarebytes_free free version of malwarebytes], [http://www.bleepingcomputer.com/download/adwcleaner/ adwcleaner], [http://www.microsoft.com/security/scanner/default.aspx microsoft safety scanner] & [http://www.kaspersky.com/security-scan kaspersky security scan].

Does deleting the places.sqlite file in the profile folder help.... SEE: http://kb.mozillazine.org/Locked_or_damaged_places.sqlite