I just thought I'd post something on behalf of everyone who's having trouble with MSN. It's being crappy. So if someone seems to be horribly inactive just based on the fact that they're never or rarely on MSN, it might also be the fact that they can't even login to their MSN accounts more often than not. I know for a fact that's what's going on with me.
Perhaps until Microsoft gets their butts in gear, it'd be best to send a PM to the member in question rather than waiting for them to come on MSN... because that could be a very long wait.