It seems there is a synchronization problem when a user change his status.
Example within Empathy :
If I look at the contact list, a user is, say, online.
When clicking on it, the icon status within the chat window says it has a different status. It can even be offline.
So there's clearly a sync problem here.
I'm using latest empathy sources but after having spoken with the developer, it's seems he's doing the right thing in order to have the status up to date.
I don't know if the problem lies within telepathy-butterfly or pymsn.