Not that long ago (certainly this evening) Apple sent out Airport Extreme Update 2008-004. This update comes days after the release of Airport Extreme Update 2008-003, which was pulled from the Software Update Catalog minutes later. Those that were unlucky enough to install the 2008-003 release got boggled down with a variety of issues. Due to all that, I don’t recommend installing this new version of the airport extreme kernel extension(s) until we see what this update’s outcome is. Personally a good sign that it’s okay for me to install will be when it shows up on the Apple Support website. Anyway, the update is a measly 2.2 MB in size, but does require a restart. Because it is so small, I don’t see the harm in downloading the update, you just shouldn’t install the update. Enjoy, Alex.
Update 1: Though the software update requires a restart and feels like it’s a kernel extension modification, it is also a hardware (firmware) update as well. It did modify the kernel_task, as the Extensions.mkext file gets modified with the update’s reboot. The new firmware version is 22.214.171.124 (it used to be 1.4.4).
Update 2: I did some digging into the exact problems of the original 003 release. It sounds like the “n” setting on the Airport Extreme Cards was permanently disabled with that firmware. It also looks like the Firewall was not functioning under 003.
Update 3: I feel it is necessary to make clear that the Airport Utility software does not get updated, so that version number will not be evidence that the update got installed. Instead, the Airport Card Firmware Version (seen using System Profiler) will tell you if the update was properly installed.