Thanks. Nice to know that XFS "should work", but unfortunalty it does not.
I don't understand your suggestion that it is not properly unmounted. Do you mean unmounted by the LS, or my Mac? This drive has been attached to the LS since it was formatted by the LS. When I tested shutting down the usb drive, disconnecting it, and reconnecting it, the LS forced me to reformat it. So I assumed it was not possible to swap between 2 usb drives.
I appreciate all the suggestions. It seems like there is conflicting info about what formats will allow read/write/delete, and how usb disks work in general. Since Buffalo will not provide complete documentation, it appears the only way to answer these questions is experimentation.
If anyone else can shed light on the behavior of usb drives with the different formats, I'd appreciate it.