Do you see this error message when you start Firefox?
That happens when the file (named places.sqlite) that stores your bookmarks and browsing history can’t be accessed by Firefox. This article covers two possible solutions.
If you don't see the error above, then you should try one of these articles instead:
The most common causes of this error are another program using the file or a problem with the file that was caused when the computer was shut off unexpectedly (like a power failure). The good news is that most of the time, simply restarting your computer and then restarting Firefox is the fix for both problems.
If restarting your computer doesn’t take care of things, you can fix this by having Firefox create a new places database for you. Don’t worry, it’s not as hard as it sounds.
Click the menu button , click help and select Troubleshooting Information. The Troubleshooting Information tab will open.
Leave the Profile folder open – go on to Part 2.
This problem has symptoms that are similar to a number of other problems. Maybe one of these articles better describes your problem.