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How to configure popular host-sharing services on a Mac

Just tried the screen sharing thing out on two Macs running Snow Leopard. When I first tried it, the login window froze and just sat there after providing credentials. It still said it was "Connecting..." though; apparently there is no time out feature on this. Despite this, if you hit the Share Screen button again, it connects just fine. The login window never goes away though. You have to manually kill it through Terminal or through the Activity Monitor--process name is NetAuthAgent.