Can't delete cited Custom Fields

I am trying to edit my posts to draw more attention to their titles for SEO ratings. I use the Suffusion Theme 3.3.1, the Platinum SEO Pack 1.3.3, and SEO Title Tag 2.3.3 programs to help me with this function. While working from the Edit Post controls for each post, I’ve encountered a problem. I can’t seem to delete the description and keyword fields from the citations for Custom Fields. After I select the “delete” controls for these fields, they disappear, and so I update the Post’s file, but when I return to the Edit Post controls for the post these fields and their values are still there. I’m just trying to learn how to setup these programs, so this is very confusing to me. Please give me simple instructions for correcting this problem. Thanks.