ath0 IEEE 802.11 ESSID:"GIGABYTE"
Mode:Managed Frequency:2.422GHz Access Point: FF:FF:FF:FF:FF:FF
Bit Rate:1Mb/s Tx-Powerff Sensitivity=0/3
Retryff RTS thrff Fragment thrff
Encryption keyff
Power Managementff
Link Quality=0/94 Signal level=-95 dBm Noise level=-95 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0
Notice that your Link Quality=0/94
This means you aren't connected.You'd get the same results if you set your
essid to any random string.

iwconfig ath0 essid GIGABYTE channel 6 mode Managed
You should have quotes around your essid.i.e.

iwconfig ath0 essid "GIGABYTE" channel 6 mode Managed

I had issues with irq's not be alotted properly.This was on with a Compaq
laptop,though.
try
dmesg | grep "wants irq"
try "cat /proc/interrupts"
put your card in the slot
"cat /proc/interrupts"
With mine,yenta and ath0 end up with different irq's.
If they are on the same irq,things could still work,though.
What you want to look for is ath0 being on the same irq as some other
module.Irq sharing works,sometimes.It just depends on how well knoppix
handles your hardware.Do you have to use any cheatcodes to get knoppix
to boot?Does your laptop have acpi?If acpi works,you should have a /proc/acpi
directory.acpi helps knoppix setup your irq's on boxes that support it.
Boot with knoppix26 and watch the boot messages.Look for acpi or apm.

As far as "iwlist ath0 scanning" goes:
After rebooting or resetting the card card,in this order,run
"ifconfig ath0 up"
"iwlist ath0 scanning"