Hi Silvia, <br />Sorry you are having problems. The System for storing this information seems to be a bit fragile. When trying this Please ensure you bookmark anything open, and close any unnecessary tabs, and do not leave any work in progress,initially you could loose more than just pinned tabs. Once things go wrong multiple sessionstore files may be created, clear any duplicates by follow these instructions: #See this for instructions on finding the profile. Use the Troubleshooting Information page, whilst Firefox is open [[Profiles - Where Firefox stores your bookmarks, passwords and other user data#w_how-do-i-find-my-profile]]#w_how-do-i-find-my-profile # Ensure everything is backed up or bookmarked and close Firefox #Delete any duplicated ''sessionstore''.js files found in the profile. Ones with a number or.bak <br />As mentioned in http://kb.mozillazine.org/Firefox_hangs#Multiple_sessionstore.js_files #Restart Firefox, you may have lost some information i.e. pinned or other tabs #'''In future''' when shutting down Firefox always use the menu option, that is from the Firefox button in a Windows machine. Do not kill processes, or close the final Firefox window by using the Windows icon in the upper right.