Hi There, I have two ideas: - the HFS FST is not patched. Your GS/OS installation may not behave well with HFS disks. => Get PATCHHFS.SHK @ http://mirrors.apple2.org.za/ground.icaen.uiowa.edu/apple16/System/Patches/ - your disk is damaged. => Please validate the disk from the Finder or from Advanced Disk Utility. Antoine