eCart Display Manager will not add Columns
For some reason, my eCart Display Manager will not allow new columns to be added to the display.
In Step 2: Configure the columns of your cart.
When I click on "Add", the list of all my columns comes up, but selecting any of them only closes the popup and nothing is added. I've done this so many times before without any trouble. Am I missing a step? It happens whether I delete an old display and try to insert a new one, or if I create a new page.
Using eCart 5.0.7 on Mac OS X 10.7.5