digsim, a forum member, had found himself unable to to use Region X under Leopard with his region free DVD drive. But he has succeeded at fixing the problem:
The solution is very simple. It suffices to delete the ~/Library/Application Support/DVD Player directory and the ~/Library/Preferences/com.apple.DVDPlayer.plist file. After running Region X again, and modifying the zones, DVD Player will now be aware of the new settings.
[translation by jwa]
