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Firefox will not open. It says Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system. I have restarted my computer multiple times


Help please

Additional System Details

This happened

Every time Firefox opened

This started when...

Today. No new items were installed or added.


  • User Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/535.2 (KHTML, like Gecko) Chrome/15.0.874.121 Safari/535.2

More Information

SafeBrowser 550 solutions 2392 answers

Sounds like Firefox is "hanging at exit". That problem is frequently caused by an Extension or a Plugin. Read all of the following articles.

NOTE: Establish a habit of exiting/closing Firefox with Firefox button > Exit or File > Exit to allow an orderly shutdown of Firefox and closing of all of the files that Firefox has open.

  1. Stop the Firefox process:
  2. Why Firefox may hang:
  3. Use Firefox Safe Mode to find a problem with an Extension or Plugin:

If this reply solves your problem, please click "Solved It" next to this reply when signed-in to the forum.

Modified by SafeBrowser