Comment 4 for bug 596064

OK, so the issue seems to be that << testparm -s --parameter-name='disable netbios' >> sometimes fails (or returns 'Yes') when started at boot-time. The "start on (local-filesystems and net-device-up IFACE!=lo)" should however be late enough...

To confirm, could you try with:

pre-start script
  date > /tmp/nmbd-upstart.log
  NMBD_DISABLED=`testparm -s --parameter-name='disable netbios' 2>>/tmp/nmbd-upstart.log`
  echo "Output is $NMBD_DISABLED" >> /tmp/nmbd-upstart.log
  [ "x$NMBD_DISABLED" = xYes ] && { stop; exit 0; }
  install -o root -g root -m 755 -d /var/run/samba
end script

And post the resulting /tmp/nmbd-upstart.log when it fails ?