So as I understand the Firefox is already running, but is not responding. Interactions between certain Internet security software (firewall or anti-virus) can cause Firefox startup hangs on some systems. A Firefox update or security software update may resolve this problem. You can also try to reconfigure your firewall or disable your antivirus software temporarily, to see if the problem goes away. If your Internet security software is causing the issue, contact the software provider's support site or switch to a different product.