How to solve Wordpress - Fatal error: Call to undefined function wp_get_link_cats() error

I setup a new blog yesterday and installing (uploading) the latest version of Wordpress 2.5.1 to my host. Login to admin panel, setting up user profile, themes and plugins, everything seems to be working fine. But when I try to add link, it shows the error: Fatal error: Call to undefined function wp_get_link_cats() in /blog/wp-admin/link-manager.php on line 155.

I'm shock and try Google for answer; however there is no solution for this "Fatal error". Some tips that I'm able to find is add a .htaccess file into wp-admin folder with the command line below:

<IfModule mod_security.c>
SecFilterInheritance Off
</IfModule>

But it doesn't help!!:(

At last, I found a similar solution that may able to solve the wordpress's fatal error!