“Read” access under Linux isnt equivalent to read access on windows machines. (NTFS)
In Linux, read access is only sufficient, when you know an exact filename and path. But in order to browse a directory, you need to have execute (+x) rights, too.
This is why firefly fails to start.
This takes some getting used to, especially when there is more than one user group involved 😉
edit:
Oh, Ron, btw: Firefly does run as guest:everybody on the NSLU2. This user luckily IS in the same group as the “admin” user, that normally does file uploads. 😉