Firefox Problems.

This is the second time this has happened. When I turn on my imac, firefox has erased all of my bookmarks, completely erases all of the search engines, there is no more Google G in the search bar and there is just a magnifying glass. I can't add search at all and I can't add any engines either. Why does it do this. Please help.

strange sounding problem. Have you got the latest version, and/or tried uninstalling and re-installing?