You're talking about a usb device? You were able to configure essid and wep with iwconfig?
I'm talking about a built-in pci card, a non-usb device.

My laptop is:
Dell Latitude D600
1.6 GHz Centrino CPU
1 GB RAM
Intel Pro 2100 Wireless card
40 GB HDD
ATI Radeon 9000 graphics (32 mb)
DVD/CDRW

I'll try Knoppix26 today and let you know if it works.