On Windows, start the Task Manager. (Other systems may have different names and / or commands). Select Processes. Look down the list for Firefox. Right click and select End Task. If this problem keeps coming up, ask for more help.

Tried that before posting question - did not help.

hello DragondHN

Can you please confirm if there is at all a background process running . As already suggested,can you please open up TaskManager,look under the Processes/Details tab for any instance of firefox.exe,i would suggest you to go through the whole list.

Try to delete the parent.lock file in the Firefox profile folder.

• C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\

"AppData" (XP: Application Data; Mac: ~/Library; Linux: ~/.mozilla) is a hidden folder.

• http://kb.mozillazine.org/Show_hidden_files_and_folders

• http://kb.mozillazine.org/Profile_in_use
• https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding