I struggle to access wireless points, and I only have a problem with Vista and not XP.
I use approximately 4 locations on a regular basis, and sometimes the network is picked up and the system says I’m connected to the net but in fact I cannot access the net.
When I try to connect to a wireless network, the network & sharing centre takes forever to connect. It later says I'm connected local only - no internet. Also, it mentions that it's a public network, and/or unidentified network.
IPV6 is off as well.
You might want to try another wireless adapter such as USB wireless dongle or wireless adapter card for laptop. Test it with another adapter to see if it will connect to your wireless network.
Also, disable your internal wireless via Device Manager before testing with external adapter.
Another suggestion is to change the channel on your router wireless setting to something else instead of Auto.