You may want to try updating the Wireless card drivers first. It's usually the easiest thing to do first, since it wouldn't require potentially re-configuring your entire network.
Try setting your router to b/g/n. The device you are trying to connect may not support N. Older WiFi adapters will see N only networks but WILL NOT CONNECT.
Make sure your computer is set to automatically get an ip address and not using a static ip address.
