Okay, I had the same problem, but I was actually doing it right. What I did before (when it didn't work) is, I would only change one of the permissions files. In order to get permissions to work on your world, you have to copy the permissions into both the [global groups/users] and the [world groups/users]. So, just take the one you think you did right... and copy it, then paste it in the world folder (with the correct name, of course). Hope this helps you, as it did me! Good Luck!
