Have you got a firewall on your wireless modem? Have a look there and make sure that you've enabled a suitably wide range of IP adresses (usually a chunk of the range 192.168.0.1 to 192.168.0.255).
Does the laptop have ZoneAlarm or similar installed? if so check in there that there's nothing blocking connection.
Is this simply for internet access or do you have a home network set up so that you can share files/folders/printers etc.? If the latter, the firewall/ZoneAlarm stuff is most likely.
ST