Sounds like someone is routing your network, people with unsecured lines tend to experience this. When someone is on a laptop, they can use a router to steal wireless service, usually neighbors.
There\'s a way to encrypted your network to prevent this from happening, hope this helps:
http://www.pcworld.com/article/130330/how_to_secure_your_wireless_network.htmltime warner repair | time warner billing | time warner customer service | time warner credit