When I try to open Firefox after I turn on my pc, I get a message saying "Firefox is already open but not responding" and then it tell me in oder to open it I must close it or restart my computer. This happened after it crashed while I was in process of closing my computer down last night. I have completely shut my computer down and even unplugged it and am still getting the same message. Please help. I just want to close it now and see if it will restart.