Many sites have the option to log in and remember you for a time period, usually a couple of weeks. For instance, Delicious, GMail, and Twitter all remember that I’ve logged in and only make me log back in after a couple of weeks even if Firefox is shutdown, crashed, or the computer is rebooted. That is, until last week when I noticed that every time I went to one of the sites I had to log in again even if I’d checked the "remember me" box. Naturally, I assumed a cookie problem.
As it turns out, if this is happening to you, a file called cookies.sqlite is damaged. Close Firefox! Right click on the START menu and open Explore. You may be navigating to some hidden directories so once Windows Explorer opens, go to the Tools menu and choose Folder Options. Go to the View tab. Make sure the bullet is on "Show hidden files and folders" instead of "Do not show hidden files and folders" Personally, I would recommend removing the check from "Hide extensions for known file types" Now navigate to this directory: C:\Documents and Settings\{username}\Application Data\Mozilla\Firefox\Profiles\ Note that C will be the letter of your drive where windows is installed and it may not necessarily be C. {username} will be the name you use when logging into windows. Once in that directory, find your profile directory. It will probably be the only subdirectory and most likely will be a bunch of random numbers and letters dot default like 2fwe34ccc.default. Go into that directory. Find the file cookies.sqlite and delete it. Restart Firefox and your problem should be solved.
