Checkout not working for some users with IE8

Unfortunately I am still experiencing this error. I have upgraded to Joomla 2.5.3 and have the latest version of Hikashop. I have the AJAX buttons turned off and have configured the P3P policy according to the link you provided but am still having problems with some users (all using IE) unable to complete their order. They are able to submit their address and shipping information (create user) but are unable to submit their order. My checkout workflow is login_address,coupon_cart,payment_shipping_cart_status_fields_confirm,end. Any help would be greatly appreciated! Thanks!

I don't have any other ideas. We have no problem with IE and HikaShop for the checkout on our end. And if we can't reproduce the problem, we cannot fix it