It won't help, Luis: it's a bug in fsaclctl, a command-line tool under Tiger. You can see it yourself with:
Code:
sudo fsaclctl -p /Volumes/Backup -d
It returns an I/O error under 10.4.x on some systems (like yours) when it shouldn't.
Working on it. You can use 2.5 or 2.1.4 until we get it taken care of.