I've installed WordPress three times without troubles.
Today I've tried to install it in the root directory of my website, everything seems to be Ok during the installation but when it reachs Step 3 I get this error:
Fatal error: Cannot use object of type stdClass as array in /home/pop-page/public_html/wp-admin/upgrade-functions.php on line 705
PHP version 5.0.0.
You can see the complete PHP confihuration at http://pop-page.com/info.php