In fact it's a bit strange, it works even by launching "planeshift" as root now... Maybe due to an upgrade of something since the last time I tried. But the message is still there when I close the game.
I will try to properly re-install the game and see what happens (also shortcuts desappeared in the menu).

Anyway, at least I can play now, thanks for your answer

Hello (please excuse my bad english),

I had the openal problem but extracting libopenal.so.1.8.446 from the karmic package, etc... worked fine.

But now I have another problem when I click "Play" I got this message :
libgcc_s.so.1 must be installed for pthread_cancel to work
Abandon

I found this on the internet about this error on Ubuntu (https://bugs.launchpad.net/ubuntu/+source/pound/+bug/40285) :

"the error:

 libgcc_s.so.1 must be installed for pthread_cancel to work

is printed by applications using pthreads and calling:

set the thread to check or cancel:
thread_setcancelstate (PTHREAD_CANCEL_ENABLE, NULL);
        pthread_setcanceltype (PTHREAD_CANCEL_DEFERRED, NULL);

and then in a tight loop try to lock a mutex and call test cancel like:
while (pthread_mutex_trylock (&progress_lock) ==
                               EBUSY)
                                pthread_testcancel ();

if the thread is exited because the parent thread sent a pthread_exit (NULL); for instance, you will see that error.

gcc thinks that this file is in:
$> gcc --print-file-name=libgcc_s.so.1
/lib/../lib/libgcc_s.so.1

and not /lib/libgcc_s.so.1. though the path should really point to the same file in the end.

This error is fixed by adding /lib to /etc/ld.so.conf and running ldconfig

I tried adding /lib to /etc/ld.so.conf and running ldconfig but there is no change.
It seems that the bug is closed without solution.

Any idea ?

Thanks in advance