current morphos versions have some problems with some usb devices. try to connect the drive directly to the peg.
also buy a via usb 2.0 pci card for the peg, usb 1.1 speed is too slow.
i have no problems with morphos and usb devices with the exception of a nokia e(n?)90 mobile (and usb hdd but that was the problem of ntfs filesystem - morphos doesnt recognise ntsf partitions despite the installed ntfs fs - not morphos' usb stack.)
DEAD pegII/G4@1000.1gb ram.radeon 9200pro
240 gigz hd.nec dvdrw.MorphOS 2.4 DEAD
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amiga1200T.blizzardppc@180/040@25.96megz ram
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zx.spectrum@3.5