Can see other wireless networks but not my own

3 computers on home wireless network. Desktop, laptop and netbook. Only desktop connects OK. laptop and netbook can see other networks locally but not my own. All was OK till recently. Desktop & Laptop run on Windows XP Pro SP3, netbook runs on linpus Linux.

Yes the wireless LAN switch is on at both non-functioning machines. All are set to correct settings, Router is set to mode G only, channel 13 and is set to broadcast SSID and act as DHCP server and DNS server. Device manager shows no conflicts on laptop. Latest wireless LAN card drivers loaded.

Firewalls turned off makes no difference.
Any ideas please?