firewall WILL make a difference,,,
trust me it's my job
to setup wireless follow thses simple instructions
1 turn ALL firewalls off
2 setup a SSID on router, win NO security
3 setup clients with same SSID, make sure you can now browse the internet
4 add WEP security on router with 26 key
5 now add same key to cleints, re check you can still access interent
6 if you have MAC security on router now is the time to add that
7 on router turn off broadcast SSID
8 download porn and have fun