•VLC: XOpenDisplay() failed shm_open() failed: Permission denied
Sometimes your audio output is just stopping? Even in the middle of the song you are playing at random times?
If you run into this problem and get the error message in the headline (or similar: shm_open() failed: Permission denied) there is a simple solution! Just add the following line to your /etc/fstab file:
shm /dev/shm tmpfs nodev,nosuid,noexec 0 0
After that type (as root):
$ mount shm
After these steps the error should disappear and you can enjoy your music again 
I ran into this error with my vlc audio server on ubuntu lucid server with vlc luggage and pulse-audio.
thanks to: http://forums.gentoo.org/viewtopic-t-691844.html
UPDATE: This fix doesn’t solve the problem with random audio cut offs. I got finally rid of this annoying problem by uninstalling pulse audio and using vlc with alsa.