When this plugin is active, it adds this line to the head of all pages in admin:
<link rel="stylesheet" href="/wp-admin/css/upload.css" type="text/css" />
This was probably not intentional so I'll skip all the reasons why it's a bad idea. The issue is that it fills up error logs and puts additional HTTP requests to the server unnecessarily.
In fact, here's a rewrite of your wb_admin_css function which uses the WP API better: http://pastebin.com/JFxDVHcD