Lemon13 has some interesting questions for you...
You said, "is picking up the correct outside IP from my ISP". I'd have expected your router to issue an IP Address to the laptop, not your ISP! Sure, your ISP will issue you an IP Address, but the router takes this, and then usually issues, say, 192.168.x.x addresses to your attached PCs assuming DHCP is running.
You said it works if you hook up an Ethernet cable to the router. Does the laptop get a similar IP Address to that issued when you try and work wirelessly? Or is the wireless connection getting something like 169.254.214.89 ? The 169 address is a default, which usually indicates a physical connection to the router, but a DHCP address either hasn't been issued or isn't being picked up.
Is DHCP within the router limited to the number of addresses that it will issue? Do you perhaps need to put in the MAC address for your laptop? Are your room mates using wireless or Ethernet cable connections? You could try turning off the router for 3 or 4 minutes, and then see after it's booted up again if it will issue you with an IP Address...
ROGER - G0AOZ.