This might be a bug for the new WordPress 2.5 or a bug in the themes of WordPress 2.5. So if you’re a Malaysia WordPress theme designer, take special note of this WordPress fatal error. I experienced this error only after activating a new WordPress theme. And it wasn’t right after activation. It was when I wanted to access the Dashboard from the blog.
When I clicked back to the Dashboard, I was greeted by this scary fatal error:
Fatal error: Call to undefined function wp_register_sidebar_widget() in /path-to-blog/wp-admin/includes/dashboard.php on line 31
Thankfully, there was already a solution online at the WordPress support. But the solution posted there came from another person; Tom Raftery. His research pointed him to another article relating to how the new K2 theme breaks WordPress 2.5.
And, apparently the cause of this WordPress fatal error:
…is because K2 turns off WordPress widgets in favour of its own widget manager and as 2.5 has started to widgetize the Dashboard, you get this error.
Which is why I would advise all Malaysia WordPress theme designers to take this down. Just in case you’re designing based on K2, or having face this WordPress 2.5 fatal error; call to undefined function wp_register_sidebar_widget().