Hy Ian
It's maybe a little bit late, but I had the same problems getting a cisco aironet 340 ( AIR-PCM342 to be exact) to work.
I'm currently using delilinux 0.61, a small linux distribution for old PCs (<16MB of RAM). It uses the 2.2.26 kernel and the pcmcia-cs-3.2.7.
I tried a lot of stuff (kernel recompile, using the AIROLINUXv15000
Linux-ACU-Driver-v2.0, using pcmcia-cs-3.2.8, IRQ settings,...) and also searching on the web wasn't helpfull at all.
My solution to this was just to downgrade the firmware of the Aironet 340.
Initially I had v5.30.17 which was perfectly working on a windows 2K laptop,
then I downgraded to 5.20.17 and 5.02.19 with no success and finally I used the 4.25.30 firmware. It worked!!!
Hope this helps!
Regards,
Dominique