After Having installed Mavericks, my iMac starts up and when I get to the log in screen I cannot type as my keyboard (which is definitely connected) is controlling the mouse, however when I try turning this off by pressing the option key 5 times, nothing happens. I have tried restarting but it won't fix. Sometimes it lets me type for a couple of seconds before I hear the sound indicating mouse keys is on and then I can no longer type. If I had a short password I could type it in fast enough, but mine is too long for this. I have no idea how I would fix this this without being able to log in.