Items will add to the cart but once the Cart or Checkout page is actually viewed/clicked on, all of the items disappear and the Cart shows as "empty."
The cart preview tab on my navigation bar will also reset to $0 once the Cart is viewed. The thing is, if I go back and add another item to the cart all of the previous items added show up again in my "cart preview" and a new total is tabulated. Once I view the actual page though, it resets to zero again and the cart is empty once again.
This is for all items, not just variable products.