Well, I have been running Mavericks on two home iMacs; a Core2Duo early 2008 Penryn, and an Late 2009 i7 model. Prior to updating these two machines, I was able to enable screen sharing at will. From Snow Leopard to Mountain Lion, I never encountered a problem with screen sharing between either of these machines. Now with Mavericks it's a 'bag o hurt'. I am always greeted now with a nasty-gram as seen in the attached thumbnail. Yes Screen Sharing is enabled and so is the network connection. I am able share folders by way of afp, so I am certainly at a loss about why this happening. By the way, both Mavericks installs were clean. Anybody able and or wiling point me in the right direction is much appreciated.