Can you clarify something. Is it just bookmarks that you are having problems with, or do you get this problem when clicking on links or typing an address in the location bar. If it is just bookmarks, a possible cause is a damaged places.sqlite file (the file that stores bookmarks), for details on how to fix that see http://kb.mozillazine.org/Locked_or_damaged_places.sqlite If it is clicking on links, being re-directed on search engines etc, then this can be caused by malware. Try running several malware scanners. It is best to run several as each will pick up things that the others miss. Some scanners you can try are: * [http://www.malwarebytes.org/mbam.php Malwarebytes] * [http://www.superantispyware.com/ SUPERAntiSpyware] * [http://www.lavasoft.com/products/ad_aware_free.php Ad-Aware] * [http://www.microsoft.com/windows/products/winfamily/defender/default.mspx Windows Defender] * [http://www.safer-networking.org/en/home/index.html Spybot S&D]