If you're running the game on Windows Vista or later, you're probably encountering problems due to protection on the Program Files folder. An easy fix is to move the file somewhere else - the desktop, downloads folder, or My Documents, for example - make the changes, save the file, and then move it back to the game folder.
When NBA Live 2004 was first released and we were all still running it on Windows XP (or for that matter, Windows 98, 2000, or ME), this obviously wasn't an issue. Now that there's more security on the Program Files folder and tasks that require admin privileges in more recent versions of Windows, it's something we'll run into from time to time.