tmp path not reachable?
Also make sure that the temporary path for uploading files is actually reachable. Your php.ini may refer to a temporary path that is not reachable from your webserver, if the server is running in a chrooted environment. If this is the case, you will get the message “PHP Warning: File upload error – unable to create a temporary file in Unknown on line 0” if error logging is enabled. Change the file_upload_path to one which is reachable by your webserver, such as ‘/var/www/temp’ in a typical Apache environment.