Hard-lock files impossible?

[spooky-mac]

Running Dapper with all packages up-to date. I want to hard lock some files, using the well known sudo chattr +i /path/filename from a terminal, but the system tells me:

chattr: Inappropriate ioctl for device when reading flags in /path/filename

What's wrong here? It did work in previous versions of ubuntu.... anyone else having this problem? How can it be fixed?

[llamakc]

Same thing here. Works as root or with sudo though.