I have a Mac mini which is my main server. I also have a few MacBooks that connect regularly to it via screen share to do things. For as long as iCloud has been around the Macbooks simply connect via screen share via the apple ID. In other words I have all my Macs with the same ID. So they have networked seamlessly. Some of them cannot connect via screen share anymore. I says "Authentication failed to "<Mac Mini>". "Please try again with different credentials". I have all File Sharing and Remote Management set to ON in the Sharing settings as well. Everything has worked up to the 10.8.5 install. I have reset iCloud on all the devices. No luck. It seems the mini has some sort of issue with the Apple ID attaching to it.