I just updated to WooCommerce 2.1.0 today and I am having a serious problem right now. Adding a variable product to cart fails. Many users are writing about it (see also: gitgub or official develop.woothemes.com website).
Variable products won’t add to cart Because some themes still bundle old files for the add to cart template being used for variable products, adding a variable product to cart fails. This should be solved by the theme developers by updating the template file. A quick solution is to delete this file from your theme directory: /woocommerce/single-product/add-to-cart/variable.php This will make WooCommerce use the new bundled template file and your variable products will add to cart again. Once your theme developer updates your theme, please check if it actually works as that will overwrite this change again.
Can you help us to solve this problem?