Please make sure that you have the hotplug and fxload packages and some
recent release of ALSA installed (see the README for the URLs).
(Check that /sbin/hotplug and /sbin/fxload exist, and that
"modprobe snd-usb-audio" works.)
When you plug in the 4x4, there should be some messages in
/var/log/messages: new device connected, firmware loading, another new
device, loading of snd-usb-audio.
If it doesn't work, please post the last few messages.