How come XBox Live randomly decides that it can't see any of my friends online?

Usually it shows my friends online perfectly fine, but whenever we're planning on playing a game together it conveniently decides to make them all appear offline and refuses to receive messages too. What's the problem? It didn't start doing this until recently and nothing has changed about my setup.

My 360 has been doing that for awhile. Also ill click on someones gamer profile and it will take a few seconds for there information to come up. Not sure what causes it but thought it may be hiccups in my connection...