yes the 3100 sees the device and puts up the do not disco, but, this is a big but, it looks like its charging, which is NOT a good thing.
did this with an ipod mini
showed up in fdisk as
/dev/sda1
/dev/sda2
hope this helps, btw is it really charging or is this just what goes on when it sees that its plugged in? This would be nice as an external hdd for my movies, but dont wanna burn up my z.