Shoutbox

So before, when you switched users with MSN locked, your sister could log in, use msn, and when you logged back in, nothing had happened to your MSN?

If not then polygamy might solve the problem www.stuffplug.com. It's a plugin for plus! and has a feature to run multiple instances of MSN at once. I'm not sure if this is the problem, but it might be worth a try.