This should help get you started or resolve problem, feedback will be needed.

Not saving History (Tools -> options -> Privacy), make sure you are not clearing Bookmarks and History in "Settings for Clearing History"

• http://img232.imageshack.us/img232/4928/clearcachew.png

If you are browsing in Private mode you will not be recording either

If you just lost your history within 1-5 days of use (1-10 days if new defaults) you can restore from a backup file

• Backing up and restoring bookmarks - Firefox - MozillaZine Knowledge Base
  http://kb.mozillazine.org/Backing_up_and_restoring_bookmarks_-_Firefox

If you created a new profile, you would have nothing from before, no bookmarks, extensions, cookies, history. If you did your old profile should still be there unless you replied to something to delete it. To find older profile with dates on places.sqlite and within bookmarkbackups folder in another profile check out each profile for last used dates -- don't try opening files, just look within folders.

1. type about:support into the location bar
2. click on "Open containing folder" button:
3. note the filename it contains your profile name
4. go up one directory to "Profiles", can check within dates each profile

also see https://support.mozilla.com/questions/838397

I have not changed any settings or changed my profile from previous version of Firefox 4 . all I done was checked for update, downloaded and applied updates, as I have done dozens of times before. Since then I have not been able to save any new book marks. I click Firefox, hover over Bookmarks with yellow star then click "bookmark this page" which the yellow star is greyed out and nothing even though the bar does highlint on selection. Also there is no history showing since my update.

A possible cause is a problem with the file places.sqlite that stores the bookmarks and the history.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox

I managed to solve the problem only by uninstalling Firefox completely and cleaning up with C Cleaner and doing a fresh install. works a treat now but lost all my bookmarks. Not really concerned about them as they were needing a clean up anyway as there was way too many.