There is a bug in Internet Explorer 10 that causes almost all jQuery and AJAX calls to fail, when used on both Windows 7 and 8. This causes a lot of issues within WooCommerce, especially when it comes to adding products to cart.
Important: It’s an issue that is impossible to work around, until Microsoft fixes this bug in an upcoming fix release.
There are also numerous reports about external software hooking into Internet Explorer, like “Free Download Manager” and “Download Accelerator Plus”. These claims have never been confirmed to actually be part of the cause of this issue.