Actually, the same thing happened yesterday with my brother's account: Because I'm a WLM tester and I have installed it on the laptop, he cant use WLM, so he uses Windows Messenger instead...
So he signed in WM, and he left it open.
Then, because I used the laptop that time, he went to the desktop computer and signed in with MSN Messenger (i havent installed WLM there), and I didnt got signed out from WM!
I could see his contacts online, see his nick changing because he changed it while he was using MSN, but I couldnt talk with any of his contacts, and I wasnt receiving his messages...
Weird
/ 
