Probá con Onyx, sino acá tenes la solución.
La encontré acá: http://forums.macrumors.com/showthread.php?t=19781
Te interpreto. Abrí el Terminal y poné esto:
cd .Trash - si no funciona entonces cd ~/.Trash
sudo chmod 777 *
rm -f *
Si eso no funciona entonces hacé esto primero y después repetí:
Just because you are logged into an administrative account, does not mean that you have root priv's. You could set your root password (Applications -> Utilities -> NetInfo Manager ->Security Menu
You will need to authenticate, enable the root user, set a password. Then you can log out, log in as root, and try to empty the trash.
You can open your other users trash folder in the gui by using either the Finder -> Go menu, or terminal.
In go menu, you can select "Open Folder" and type in ~username/.trash
or in the terminal "open ~username/.trash
where username is the username of the user with the trash (obviously)
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