After much time on the phone with the bloody Lucent people, some nice fellow managed to track this down for me.
EVERYONE: UPDATE YOUR WEB PAGES!
Both the wavelan2_cs and wvlan2_cs drivers (the Lucent and GPL drivers, respectively) work and intercommunicate just fine ONLY if the "Station Functions Firmware" on the WaveLan/IEEE card is 6.04. Note that the latest firmare release is 6.06.
If you update your cards, then windows boxes will be able to communicate, but nothing will talk to Linux.
Not only Linux, but you can't even talk to Lucent's own Wireless Ethernet converter.
Everything will work if you have an access point, if you use the 6.06 (but I haven't tested this).
The problem is that in going from firmware 6.04 to 6.06, Lucent REMOVED support for the non-IEEE "ad-hoc" mode, and replaced it with a fully-IEEE "peer-to-peer" or "IBSS" mode.
I ranted quite a while at them over making incompatible firmware changes...
While you're at it, you can only use the 6.04 firmware with the 6.00 drivers for Windows on a windows box.
Here are some useful URLs...
The firmware: FTP://FTP.WAVELAN.COM/PUB/SOFTWARE/IEEE/UPDATE/FIRMWARE/CARD/WIN/wsu10604z.exe
The Win2000 driver: FTP://FTP.WAVELAN.COM/PUB/SOFTWARE/IEEE/PC_CARD/WIN2000/v600/wlw2_600.exe
The Win95/98/NT driver: FTP://FTP.WAVELAN.COM/PUB/SOFTWARE/IEEE/PC_CARD/WINDOWS/v600/wlwi600a.exe
There's an apple driver on Lucent's "download" site as well (http://www.wavelan.com/).
This saga is officially over. Everyone should email Lucent (mailto:email@example.com) and vent their displeasure.