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Firefox problems

Firefox is reporting "Firefox is already runnning but not responding. To open a new..."

There are two possible reasons for this error message:

Another Firefox session is still running on another computer, or the application has shut down abnormally because the computer crashed.

If no Firefox session is running on another computer, you need to delete the orphaned lock files in the Firefox profile. Under Linux:

  • stop the current Firefox session
  • open a Linux terminal
  • change to the Firefox profile folder:
    cd ~/.mozilla/firefox/<profile>
    is a random 8-digit sequence followed by .default (if several profiles have been created you need to check in file ~/.mozilla/firefox/profile.ini under which profile default=1 can be found
  • delete the two lock files in the profile folder:
    rm lock .parentlock

Under Windows the lock files parent.lock are placed in

After removing the lock files, you should be able to start Firefox without receiving an error message. If your bookmarks have disappeared, please find the solution below.

"My bookmarks are gone!"

If the bookmarks are empty, you can recover them using the Firefox backup. Under Linux:

  • stop the Firefox session
  • change to the Firefox profile folder (find details above)
    cd ~/.mozilla/firefox/<profile>
  • delete all places.sqlite* files
    rm places.*
  • Check in sub-directory bookmarkbackups whether it contains files of size 0 and delete these
    find bookmarkbackups/bookmarks*json -size 0 -delete
  • restart Firefox
  • the bookmarks should have been restored by now, otherwise you can select one of the versions offered (normally you will select the most recent one) at Bookmarks -> Manage bookmarks... -> Import and save -> Restore

Under Windows proceed analogously. Here, the profile directory is placed in

"My Firefox browser does no longer show any PDF files or Flash videos."

In the current Linux versions the plug-in for the display of proprietary plug-ins has got a bug. These plug-ins work only once in each Firefox session.

A (not very satisfactory) workaround for both problems is to end the program npviewer.bin with killall npviewer.bin each time the error occurs.

The problem with PDF files can be bypassed by making the Acrobat Reader open the PDF files in a new window. For this you need to change the default settings in Firefox: Open Edit -> Preferences -> Applications and select under PDF document the entry Use acroread.