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Error message that old firefox is running when starting firefox

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Starting today (Apr 30), when trying to open firefox the following message appears:

"Firefox is running, but not responding. The old Firefox process must be closed to open a new window." My options are to close firefox or cancel.

When selecting close firefox, the message will reappear with the same options. I am unable to run.

Steps I have taken: Uninstall Firefox Download latest Install

Message still appears

Starting today (Apr 30), when trying to open firefox the following message appears: "Firefox is running, but not responding. The old Firefox process must be closed to open a new window." My options are to close firefox or cancel. When selecting close firefox, the message will reappear with the same options. I am unable to run. Steps I have taken: Uninstall Firefox Download latest Install Message still appears

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