I am having similar problems. I am on a virtual server and so I will not be able to change the safe mode settings.
I was able to change the permissions, but the chown changes don't seem to be recognized.
I have created tmp directories at root and in ezpub directory (which resides at root) and neither are recognized. Cannot get past these issues in the wizard.
@Fabrizio : have you restarted the webserver after you've changed the safe mode setting ? And if yes, just check the output of the phpinfo() function to see if safe mode is actually disabled.
@Jim : there is no way eZ Publish will run with safe mode enabled, the restrictions are far too important...
@Fabrizio: Could you change topic to more adequate to your problem? Currently says nothing, this will help forum readers and future users who search for similar problem.