Those are a lot of devices. How many of them are wireless?
I know I've had that problem before, when some of my wireless devices have trouble connecting and end up in some loop. And what kind of security do you use? WPA or WPA2?
And...what do your logs show? If you copy and paste it, do a search for those IP addresses. I have a feeling it has to do with wireless clients deauthenticating, and not being able to reconnect properly.