WooCommerce Variable Product in 2.4.2

My issue is with variable products.

The product add to cart button is missing and the following message displayed: Sorry, this product is unavailable. Please choose a different combination.

In the admin when viewing the variations tab, I get this error: Warning: Invalid argument supplied for foreach() in wp-content/plugins/woocommerce/includes/class-wc-ajax.php on line 2422

I notice that all of my variation IDs and details are showing in the admin, but the unique selected attributes for each variation fail to display , so I cannot tell which of the variation IDs is Medium/Red or Small/Black. Those fields simply are not displaying. Each variation shows to be enabled, in stock and have prices.

Thanks for your quick work on this!

Additionally, the default selection does display in the admin, and both of the two dropdown boxes on the product are preset to the default selections (which should display a price). Clicking on either attribute to view other available selections for that attribute on the product page wipes out both attributes and makes only choose an option visible in both dropdowns. No JS errors display in FireBug.