My guess would be that the name of the icon corresponds to the name of the device. So def_CD0disk.info will be used as the default icon for disks inserted in to CD0:. If that is true, then perhaps you had a separate mountlist for CDs and DVDs. Maybe one with a device which only works with CDs and one which only works with DVDs, and then a different def_xxxdisk.info for each device. That's all just guess work though, so could well be totally wrong