Looks like you may be mixing buttons for products priced with different currencies in your E-junkie Seller Admin.
The cart can only calculate prices in one currency at a time. This is because payment processors can only receive orders passed to checkout with all pricing in a common currency; they have no provision to handle a checkout for items priced in different currencies. Thus, if you have some products added in the cart that are priced in, say, GBP, then adding a product priced in USD would "reset" the cart and start it over with just the product priced in that different currency.
BTW, you also only need to have one View Cart button per entire page; you don't need a View Cart for every single Add to Cart. :^)
