i'd make sure you have the latest version of libusb, at least 0.1.12, anything before that is unreliable for what you're doing.
check to see if libmtp can see your device:
if that spits out your device info, then amarok should be able to see it
for mine, i created a directory /media/zen
mtpfs -o allow_other /media/zen
I got mine to work, but it was always buggy, so i gave up and bought an Archos, but maybe that will help you in some way hopefully