I'm using 404-notifier and it's reporting a 404 for a file that exists.
The file in question is the javascript for WP-Greet-Box:
404 Report - a file not found error was registered on your site.
404 URL: http://www.domain.com/wp-content/plugins/wp-greet-box/js/onload.js
Referred by: http://www.domain.com/wp-content/plugins/wp-greet-box/js/onload.js
User Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)