“Firefox is already running, but is not responding” Bug

January 2, 2009 · Filed Under Windows · Comment 

When trying to open Firefox, I often get a pretty alarming sounding error message titled “Close Firefox”. The full error message is: “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 can’t find any Firefox process running in order to close it. What’s going on?
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