Not really anything to do with his question Seph, which was that he's connected various devices directly to his modem and has now used all the MAC addresses up that he's allowed to have associated with his modem.
Could you perhaps clone the MAC of one of the laptops, preferably one you connect via wireless
to the router perhaps?
The limit used to be either 3 or 4 so you've almost certainly broken it. Powering stuff down doesn't make them go away and won't make any difference, time will.
Try the MAC cloning. I can't remember offhand the timeout.