No, I connect from either another Mac Mini or my MacBook using the standard Screen Sharing.app. This is definitely a lion server thing and started the day that lion got installed. I never saw it with Snow Leopard server. I've seen reports of the artifacts at other sites/forums but never a firm resolution. Also, I do not see the artifact when connecting to a computer that is running regular OS X Lion. I wonder if the default ARDAgent.app settings for lion server are different than for regular lion and that this might be causing the problem.