localhost ~ # uname -a
Linux localhost 2.6.19-gentoo-r5 #5 SMP Mon Mar 12 17:00:05 EDT 2007 i686 Intel(R) Pentium(R) 4 CPU 2.80GHz GenuineIntel GNU/Linux

localhost ~ # lspci | grep Bro
03:01.0 Network controller: Broadcom Corporation BCM4306 802.11b/g Wireless LAN Controller (rev 03)


localhost ~ # lsmod
Module                  Size  Used by
ieee80211_crypt_wep     8320  3 
arc4                    6016  0 
bcm43xx               416032  0 
ieee80211softmac       33408  1 bcm43xx
ieee80211              44908  2 bcm43xx,ieee80211softmac
ieee80211_crypt         8832  2 ieee80211_crypt_wep,ieee80211

localhost ~ # iwconfig eth1 key ABCD123456
Error for wireless request "Set Encode" (8B2A) :
    SET failed on device eth1 ; Operation not supported.

Messages appended to dmesg thereafter

ieee80211_crypt_wep: could not allocate crypto API arc4
eth1: could not initialize WEP: load module ieee80211_crypt_wep

Yet both of the aforementioned modules are loaded.