Yes, I did exactly as you said. Still doesn't work. Still untrusted permission. I've also tried adding root to the group games and installing, but still no result.
I tried entering planeshift (system wide install) in terminal, and this is what i get:
Segmentation fault (core dumped)
Then I tried sudo planeshift, the client shows up, offering an update, etc, but with no sound, and a lot of what seems to be error messages in the terminal. Could not open this and that, couldn't load plugin iSoundManager, etc.