It was all working fine until some point the day before yesterday, then nihil.
"Determining IP information... failed."
Using a LiveCD on the same machine works fine; using another machine works fine; iwlist works fine; ifconfig ath0 up works fine; KWifiManager shows all the right info except the IP address. Everything works except dhclient. /var/log/messages shows dhclient requesting an address and not getting any offers. I haven't a clue what could have gone wrong. I've blown away my configurations several times, but it didn't help. I've tried using Fedora's system-config-network tool and doing it manually.
I'm using Fedora Core 4, kernel 2.6.14-1.1644_FC4. lspci shows the card as:
02:0a.0 Ethernet controller: Atheros Communications, Inc. AR5212 802.11abg NIC (rev 01)

Ummmm... I don't know how to change this in Fedora, but I know in Suse, after setting up the wireless it might work great...until you reboot. If you don't have the wired card set to "on cable connection" and the wireless card to "start on boot" then you'll have issues. The problem is, the wired card boots before the wireless in basically any distro. If the wired card tries to get an ip through dhcp, but can't because it's not plugged in, then the wireless card tries to get an ip through dhcp after that...this creates problems. No matter what I tried, I couldn't get an ip to save my life. I would try either setting your wired card (assuming you have one) to only come on if the cable is plugged in and the wireless card to start on boot. If you can't figure out how, try removing the wired connection and rebooting. See if this helps...

Wired card isn't ifup'ed on boot.