I spent way too much time this morning trying to figure out which piece of CSS was causing the moused-over element in the Country and State drop downs on my checkout page to disappear. By default, the font color for the moused-over elements is white (#ffffff). When rendered on a white background, the moused-over (or highlighted) element disappears.
WooCommerce uses the Chosen jQuery plugin for both of these drop downs. I am also using the Genesis framework and found to correct the problem I had to add the following to my theme’s style sheet.
#content ul.chzn-results li.highlighted {
color: #E8192E;
}
I hope this helps someone else in the future.