I found this in plus live 4.0, but did'nt report it (my bad...)
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When your in a group chat, if you write .scr, you will get booted from the chat, with this message.
________
You are having temporary network problems and are no longer in this conversation.
________
This is my versions.
Windows XP Service Pack 2 (5.1.2600)
Windows Live Messenger 8.00.0792
Messenger Plus! Live 4.01.0.240
I've tested that it will do this , if you write .scr(and more stuff after it), and that .sc (or any less wont do it).