Line at top of borderless table

All tables created have a line across the top regardless of border settings. I have tried tracking down the source with Firebug to no avail.

This is a screenshot of the editing window on drupal.ckeditor.com with a borderless table


This is the a screenshot of the preview which is the same as published. I get the same thing on my website.


These are the settings that I used when creating the table.


Any help is appreciated. Thank you.
Shawn