One one of my systems many times when I close Firefox the system freezes up. When I am able to get Task Manager open I find that in the Processes tab (not the application tab) that firefox.exe is still running and using nearly 100% CPU. I can end the process and the system returns to normal. I was hoping someone here might have some insights as to what could be causing this. I found references in my searches to some people reporting high CPU usage while surfing with FF sometimes but nothing to do with its process remaining running and using up all CPU after closing FF. I have no problems while surfing, only upon closing the application. Both of my systems are running XP Home SP2 with almost identical software setups. Both have FF 3 (latest) with only one extension NoScript. Only the older desktop is haing this problem. Any ideas?