D-Link DWL-AG650, AirPort Extreme, and WEP

[Harald Hanche-Olsen]

I got me a D-Link DWL-AG650 wireless card (based on Atheros 5212) to
use with my AirPort Extreme (802.11g) at home.

Everything is fine if I turn off WEP.  But with WEP enabled I get the
dreaded "authentication failed (reason 13)" message.

I hope, BTW, that the error message one gets if one simply uses the
wrong password is more informative?  In any case, I checked the
password 2^n times, and feel pretty confident that I have it right.

The command I used to configure the interface is

  ifconfig ath0 inet 10.0.0.3 netmask 0xff000000 \
  ssid foonet mode 11g wepmode on wepkey 0x1234567890 debug

and the dmesg output ends with (after various sending probe_req,
received beacon & probe_resp)

ath0:      macaddr          bssid         chan  rssi rate flag  wep  essid
+ 00:03:93:ef:24:f9 00:03:93:ef:24:f9   10    50 54M   ess  wep  "foonet"
ath0: sending auth to 00:03:93:ef:24:f9 on channel 10
ath0: received auth from 00:03:93:ef:24:f9 rssi 48
ath0: authentication failed (reason 13) for 00:03:93:ef:24:f9

What I would like to know is, am I doing anything obviously wrong?
Or are there known issues (perhaps with workarounds) for this setup?

I thought I'd ask if anybody can suggest something off the top of
their head before I deluge the list with tons of debug messages.
(I know about sysctl debug.ieee80211=1 and
tcpdump -e -i ath0 -y IEEE802_11, but haven't tried them yet.)

- Harald

PS.  No need to inform me that 40 bit WEP is just a joke.
     I am only doing it while debugging my problem.