Got a new 27" iMac and am attempting to install windows using bootcamp assistant. The problem is when it gets to the installing phase and a windows screen is displayed to pick the language, neither my mouse nor keyboard are registering any input (yes they are turned on, otherwise I couldn't not have got to this stage). So I can neither proceed nor cancel the operation with neither mouse clicks nor keyboard input being recognized. If I turn it off and restart holding Option and then choose Macintosh HD instead of booting to OS X it boots back into the attempted installation of Windows, where I have the same problem with the keyboard/mouse not working. How can I get out of this cycle?