I recently upgraded my whole system using pacman and the testing-repo, switched to a 2.6.13-kernel (I used ABS and configured one using mostly the archck-stuff), solved some weird udev-issues (using the "usb-handoff" option) and thought that everything is fine. I could even get fglrx to work.
As my next step I decided to compile ieee80211 and the IPW2200-driver.
Everything works perfectly now, iwconfig says:
lo no wireless extensions.
sit0 no wireless extensions.
eth0 no wireless extensions.
Warning: Driver for device eth1 has been compiled with version 18
of Wireless Extension, while this program supports up to version 17.
Some things may be broken...
eth1 IEEE 802.11g ESSID:"home"
Mode:Managed Frequency:2.412 GHz Access Point: 00:C0:49:5A:B9:7E
Bit Rate=54 Mb/s Tx-Power=20 dBm
Retry limit:7 RTS thr:off Fragment thr:off
Link Quality=100/100 Signal level=-18 dBm Noise level=-86 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:3 Missed beacon:0
It even detects my AP!
But when I try to get an IP from my router, dhcpcd and dhcpclient fail.
Dammit, haven't been here in a while. Still rocking Arch.
You could first try to connect without DHCP and see what happens. You might also want to use ABS and compile the latest wireless_tools package.