I've done a couple more tests on my laptop about this issue, and these are what I found:
* I excluded some irq choices at /etc/pcmcia/config.opts and the problem still remains. (attempted irq 3, 9, 10)
* I tried to use iwconfig to change something less important (e.g. changing the "Nickname" or "essid" of the interface) and the laptop still freezed... So basically I could only try :
"./iwconfig" OR "./iwconfig --help" BUT nothing else in the argument could save me from cold-booting the laptop...
Thanks for your helps.