Problem with Shopping Cart

It's a bug we found out yesterday. We fixed it on our end and it will be available in next release tomorrow.
If you want to fix it, you need to edit the file administrator/components/com_hikashop/classes/product.php and add at the beginning of the function checkVariant the line:
if(!empty($variant->variant_checked)) return true;

and at the end of the function the line:
$variant->variant_checked = true;