6.x版本安裝問題

想請問一下..
再安裝完.drupal6x後..會出現以下的系統訊息:
# warning: tempnam() [function.tempnam]: open_basedir restriction in effect. File() is not within the allowed path(s): (/var/www/vhosts/osceshop.com/httpdocs:/tmp) in /var/www/vhosts/osceshop.com/httpdocs/includes/file.inc on line 756.
# 無法產生檔案。

想請問是哪裏出現問題?
反覆測試過..安裝5x的就不會有這問題出現....

請給我指點一下..
謝謝大家