Why the MacBook connects to an AP while others can't?

There's an AP in my neighborhood, to which I cannot connect with Linux or Windows XP/Vista, because it doesn't distribute IP, DNS, something like that.

But today my brother came with his MacBook, and he connected to that AP effortlessly with just one click while my computers were still unable to do that. So I'm quite confused here. Are there some special settings in OSX? Anybody could tell me?

The owner of the AP might have MAC address filtering on and blocked all of your machines but never blocked your brothers

Well, either that or he had a manual IP address set up for his Mac.

Most people leave their router's default network address, so it's quite possible he had an ip address in the correct network range.

Lots of people now also use opendns's dns service, so if he had added that as well, then that would explain it.