I had the same issue last fall. Solved it 90% by talking with the neighbors. We all stuck our access points in the middles of our basements (keeping the signals mostly going upstairs instead of sideways), we set up channels 1, 6, 11, 1, 6, 11 from door to door. We also set up WEP keys the same way, 0101010101, 0606060606, 1111111111, 0101010101 (and so on). We weren't all that worried about security, we just wanted to keep our damned connections straight. The biggest change came from putting the AP's downstairs.