There should be a [ + | - ] button bar underneath the login items list. Selecting the item in question, then pressing [ - ] should remove the item from your login items.
Yes, I've tried to delete it using that method but it's grayed out. It is listed as Unknown App, so I'm not sure what it is. Also, the MBP is running 10.8.5, not 10.7 like I listed before.