Preview has been acting up as of late, but this morning it had a major tantrum: Not only will it not open any images, it also will not "force quit." I have attempted a series of different "force quit" methods, so that I may reboot the whole system and start out fresh, but no way, nothing works. I am using a MacBook Air, Yosemete 10.10.3 and at my wit's end. My goal is to simply "force quit" preview so I can re-boot,, or either get preview to work properly again. Been all over the web trying to find help and I did locate a site showing how to "force quit" 5-different ways and none of thme worked. Help??