wpa_supplicant and madwifi - IEEE80211_IOCTL_SETMLME fails

[Chip Salzenberg]

I've been using wpa_supplicant successfully for a long time with the
hostap driver.  (It's the Debian binary of 0.4.7.)

But now I've upgraded to an 802.11g card, the D-Link DWL-G650.  I
installed the madwifi driver and plugged in the card, and so far
everything was peachy.  But when I ran wpa_supplicant with the options

   -i ath0 -D madwifi -c /etc/wpa_supplicant.conf

It doesn't work.  It mostly seems to work, it detects the correct
ESSID and tries to associate, but then there's an ioctl failure:

   ioctl[IEEE80211_IOCTL_SETMLME]: Invalid argument

What info should I provide to help you debug this?  Or is this a known
problem?

PS: I compiled wpa_supplicant 0.5.0 and tried it -- same exact results.
-- 
Chip Salzenberg <chip at pobox.com>