If you're using a computer with Mac OS X 10.4 to 10.4.2 and change a file's ownership or permissions in an Info window (select a file and then choose Get Info from the File menu), the settings will appear to change, but they aren't actually applied and saved. If you close and reopen the Info window, you'll see that the settings have reverted back to what they were before you made your adjustments.
To resolve this issue, update to Mac OS X 10.4.3 or later.
Advanced Tip: If you're not ready to update to Mac OS X 10.4.3 or later and you're comfortable using Terminal, you can use the chown and chmod commands to make ownership and permission settings changes. For more information on changing ownership, groups, and permissions in Terminal, see the man (manual) pages for chown and chmod (type man chown or man chmod in Terminal).