Product page greys out after variation selection

I’m having an issue with my product variation selections. When I click in the first drop-down to select the product variant, the entire screen greys out. I can’t seem to get it to go back to normal until I reload the page. I’ve tried this in a few browsers, so it doesn’t seem to be an issue there. I’ve also tried resetting all theme options to ensure it wasn’t something I had done.

You can see the problem here: https://millertacticalgroup.com/sandboxx/?product=229

I’ve also noticed that when I click a thumbnail image beneath the main product image, the same thing happens.

I am using Virtue 2.0.3.