Airport stops working.

[Enric Nadal <llistes_correu@telefonica.net>]

Hi,
I've been having some issues with the airport card of my ibook g3 900Mhz.
Sometimes, it stops working, but I can't trace were the problem is.
I'm using a ubuntu breezy, with a 2.6.13.2 kernel compiled myself.
The firmware of the airport card is version 8.70, as I installed Tiger to try 
it. The only strange output I get is:
Error for wireless request "Set Mode" (8B06) :
    SET failed on device eth1 ; Operation not supported.
when i ifdown it.
Any clues about this problem or anything I can do to provide more information?
Regards,
Enric.