For some time, I have trouble closing Firefox. When I try to close it a message appears: "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." It used to be that opening one of my other browsers, Internet Expl. or Netscape Navigator, would do the trick but not anymore. Now, when this message appears it seems that the only way I can get Firefox to close is by stop and restart my computer. I have called my ISP but they believe the problem is with Firefox since none of my other browsers have this problem. I have also performed system restore and deleted and reloaded Firefox several times but each time, the problem reappears. Thank you for any advice you can give me.