Fatal error when adding a link to Blogroll

Whenever I add a link on the Blogroll > Add Link page, I get this message:

“Fatal error: Cannot use object of type WP_Error as array in /…/wp-includes/taxonomy.php on line 1010”

However, when I go back to the Blogroll page, the link has been added. And none of my links appear in the sidebar even after I add “Links” widget. In fact, the widget doesn’t appear at all.

How can I:

1) Not get this error message?
2) Have the links widget appear on my index page?

Using 2.3.0
http://keywon.com/log (It’s written in Korean and English)

Much appreciated!