Describe WifiDocs/Device/WifiDocs/Device/DWL-G122 (Rev C1) here.

To make sure that your usb device is the correct, have a look at the information printed on the device. In my case, the model information reads "Model No.: DWL-G122 H/W Ver.:C1 F/W Ver.:3.00" What's important here is that the hardware version is C1 - earlier models are covered by different drivers.

Also note the output of the lsusb command, which, in my case, produces the following line:

Bus 003 Device 002: ID 07d1:3c03 D-Link System

Check the WifiDocs/Driver/RalinkRT73 page for setup this device.