[Plugin: J Shortcodes] Removing borders

I had the same problem but finally figured out it was the settings in the style sheet that was the issue. Go into your theme’s style sheet and find the section for your theme’s entry tables. It will look like this:

.entry table

Wherever there’s the border and the attributes for it, change it to this:

border: none;

That should correct it and you should be able to use jshortcode’s columns without the annoying table borders.