This usually comes as a result of incorrect floppy format. The S1000/S1100 had the ability to format Double Density floppies to High Density (and the other way round). This was before the days of drives that could tell the difference between the two disk types. Although this was great at four in the morning when all you had was a handful of DD disks and too much stuff in memory to fit onto them, formatting a low density disk to high will render it incompatible with the more recent samplers.