Click "checkout" leads to "The cart is empty" only for the first time
Every time a new customer click on "checkout", the next page says "The cart is empty"m i.e. does not direct the client to the "payment" page.
However, if the customer remain on the same browser, he does not experience this issue anymore (i.e. if he adds to cart and clicks "checkout" again - he is directed to the payment page the 2nd time). However, if he closes this old browser and opens a new one, this error happens again. The customer is using IE 6.0.
Please advise. Thank you.