I'm using my Netbook at the moment. It's connected by WiFi to the Sky router. At the same time I have 2 other Desktops connected by LAN cable. In addition I have occasionally a fourth laptop connected by WiFi. Sometimes I also connect an HTC Smartphone by WiFi. It works for any combination so I suspect you have a problem somewhere.

First of all turn your netbook Firewall off and see if you can connect. If that doesn't work then turn the firewall back on and try assigning a manual IP address for the netbook - something like with a submask of and a Gateway of (use this last one for the DNS server as wel). I have to do this for the HTC Smartphone because it fails to automatically get an IP address.

What OS are you using?