safe_mode should be disabled for eZ Publish. With enabled safe_mode there is a list of limited/disabled functions which affects eZ Publish functionality. http://pl.php.net/manual/en/features.safe-mode.functions.php
It is far better to have safe mode disabled, but I have managed to run eZ publish successfully on a machine that has it enabled by also enabling safe_mode_gid, which relaxes the file ownership check to a group ownership one. (It wasn't my choice to keep it enabled.)
