IE11 cart issue on V6

Hi, if you are shopping on the site you can add items to the cart.

When you proceed to checkout, then Login as an exisitng client the contents of the shopping cart are lost.

On testing I found that the site works fine in chrome, firefox etc, and also if you put the site into compatibility mode.

I tried adding <meta http-equiv="X-UA-Compatible"content="IE=EmulateIE9" /> and <meta http-equiv="X-UA-Compatible"content="IE=EmulateIE10" /> and even <meta http-equiv="X-UA-Compatible"content="IE=EmulateIE8" /> but this has made no difference.

Any ideas on how to resolve this muchly appreciated.

Thanks