None of these solutions has worked for me. Like many other people here and in the Apple support forums, up until the 10.5.2 update, everything was working perfectly. Now, every so often, I will just lose my connection and only on the 10.5.2 machine. It happens suddenly and randomly, many times I won't even notice it until Safari or Adium or something just tells me that I'm no longer connected to the internet. When that happens, I can see that my airport icon is completely greyed out. When I go to the drop-down menu, airport scans and I can find and select my network to reconnect. Incidentally, I've noticed that whenever I use that drop-down menu, Airport is always furiously scanning for new networks. Anyway, if I don't select manually, airport will eventually reconnect on its own. This happens at least a few times a day. I have the Airport Extreme base station and I have tried every solution suggested here and elsewhere (there are many, many people experiencing this issue apparently), including completely turning off ipv6, changing the channel used, using N only, downgrading my firmware, etc. etc. The crazy thing is that this problem still happens even without a wireless router in the mix, when I'm connected via ethernet directly to my modem, so long as Airport is turned on. So far, the only solution I have found is to connect via ethernet (with or without the router) and leave airport off entirely. This is a reasonable workaround for me since this problem isn't affecting any other wireless device in my house and my mac is close to the router, but I don't see this being a good solution for most.