Database errors on website after upgrading to WP 3.5

Hi

I upgraded to WP3.5 and got this error message that I can’t figure out so far. This error message appears ON my website, so quite frustrating for the credibility of my business…

“Warning: Missing argument 2 for wpdb::prepare(), called in /home/route32/public_html/wp-content/plugins/worker/core.class.php on line 221 and defined in /home/route32/public_html/wp-includes/wp-db.php on line 990”

Here you can see the message on top of the page
https://www.route32.be/r32v2nl/

When I go to the lines mentioned in the files, I don’t really understand what the problem is.
In core.class.php line 221 says: ‘add_link’ => ‘mmb_add_link’,
In wp-db.php line 990 says: function prepare( $query, $args ) {

I wonder if I’m looking on the wrong lines – I’m using Notepad+ as an editor, and it arranges all code nicely, but i’m not sure if the line numbers in that editor are the same numbers that the error message refers to.

Any help would be much appreciated. Thanks.