Just bought a new IMAC. It came with El Capitan OSX 10.11.1. I used Time Machine to restore all my data and information. Everything carried over fine, and all my software is working fine. EXCEPT FIREFOX - version 42.0. It hangs up with a blank screen at boot-up. Sometimes it boots and Yahoo my home screen appears, but does not recognize my mouse, and ignores my mouse clicks on everything. Sometimes (Rarely) Firefox boots up. Unfortunately if I get out, the next time I envoke it, the same blank screen etc. I tried to restore Firefox as directed on their support site, but still have same problem. Any suggestions?