I get this problem:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/231049
which means the device connects at USB 1.1 speeds. I work round the problem by connecting through a USB 2.0 external powered hub.
But I have never seen my Fuze (or e260v2) fail to be detected. Maybe your cable is flakey?
I usually use MSC mode because although libmtp supports multiple storage devices (the microSD card), none of the applications (Amarok, Rhythmbox et al) seem to cope well with it.
