At the bottom of the desktop, in the panel from which I launch applications, I have the Firefox circle icon. When I click on it, I get this message: "Close Firefox. A copy of Firefox is already open. Only one copy of Firefox can be open at a time."  However, it doesn't appear that a copy of Firefox is open.
  If you can't help me resolve this, I'm going back to Safari.
            Help!

I downloaded on my iMac the recent upgrade to Firefox. Now on my desktop, I have a rectangular icon that says "Firefox" underneath it. As instructed, I have dropped it into the Applications folder, which now contains both the rectangular icon and the circle icon. Both say "Firefox." At the bottom of the desktop, in the panel from which I launch applications, I have the Firefox circle icon. When I click on it, I get this message: "Close Firefox. A copy of Firefox is already open. Only one copy of Firefox can be open at a time." However, it doesn't appear that a copy of Firefox is open. If you can't help me resolve this, I'm going back to Safari. Help!