The iwlist scan should work so the problem may be in the driver you are using. However first, turn off the eth0 interface and try again.
Look at the output of "lspci -v". Then make note of the hardware address, which is the first thing listed in the section.
Next look at the output of "lspci -n". This listing will contain a number of the form xxxx:xxxx that identifies the hardware to the user. You can use the discription of the device and/or the hardware identifier in google to search for the driver.
This webpage may help. It looks like there are two different drivers that you can try: