After upgrading to WordPress 2.5 earlier today, I found one problem. The Popularity Contest plugin (generates a list of the most popular posts on your blog – it powers the Have you read these? list on the right) wasn’t working. Fortunately there’s an easy fix.

In the WordPress admin area, choose Plugins, then scroll down to Popularity Contest, and click Edit. Scroll down until you see this bit of code:

if (!isset($wpdb)) {
require('../../wp-blog-header.php');
akpc_init();
}

Remove one of the ../ from:

require('../../wp-blog-header.php');

and choose Update File. That’s it!

More info on this error is available in the WordPress Support Forums.