It seems like your PHP is configured with the open_basedir setting. See http://www.php.net/manual/en/features.safe-mode.php#ini.open-basedir for more information. I advice you to turn open_basedir off.
It's better that I don't modify this value... Do you think I can ignore safetly the warning? Basedir is "locked" on root directory of my site, for eZ publish should be enough... It's correct?