rMBP running 10.8.2 and a G3iMac running 10.4.11 Tiger. When I try and use Screen Sharing on the MBP to connect to the G3 it prompts for both a username and password. I enter a valid user and pw but it fails with Authenication failed to "Ruby". Please verify you have entered the correct name and password. Third-party VNC clients, e.g. JollysFastVNC on my MBP and Remoter on my iPhone, can connect fine, but they only request a password. Any ideas?