Let me make sure I understand your question. You have a wireless router that has an Ubuntu system connected to via cable and your laptop is accessing the router via wireless. If that is the case, the Ubuntu system should have nothing to do with your laptop's ability to stay connected to the router. If you are running XP, however, there is a "pecking order" of wireless networks. XP will try to connect to networks in the order they are on that list. If your neighbor's access point is above yours on the list, XP will make every effort to stay connected to it before doing a fail-over to yours. If you look at the list and that is the case, try moving your network to the top of the list.