Unknown username: "wordpress" as adminstrator?

Unfortunately this sounds like a script has been added to your site to create this user, so would suggest that your site has been hacked.

If this is the case, you need to start working your way through these resources:

• http://codex.wordpress.org/FAQ_My_site_was_hacked
• http://wordpress.org/support/topic/268083#post-1065779
• http://smackdown.blogsblogsblogs.com/2008/06/24/how-to-completely-clean-your-hacked-wordpress-installation/
• http://ottopress.com/2009/hacked-wordpress-backdoors/

Additional Resources:

• http://sitecheck.sucuri.net/scanner/
• http://www.unmaskparasites.com/
• http://blog.sucuri.net/2012/03/wordpress-understanding-its-true-vulnerability.html