If you were using Buy Now buttons, those bypass our cart and take buyers directly to instant checkout for just one item at a time, so any lag or delay in page-loading there would typically be at the payment processor's end (e.g. PayPal).
If you are using our standard E-junkie Cart buttons, you should include at least one complete block of View Cart code from your Seller Admin on every page where you have any number of Add to Cart buttons. The View Cart code manages the nice overlay-style cart display "inside" your page, but it has to be on every page in order to work.
If a page is missing the View Cart code, or if that code is incomplete or gets garbled somehow, then our cart buttons will still work in "fallback" mode, by popping-up a separate window/tab to display the cart. The non-JavaScript version of our cart button codes, which you can obtain from Seller Admin, also use this pop-up cart window/tab. However, items added to this popup cart would not show up in the standard overlay-style cart, and vice-versa, so you should make sure all the pages in your site are using one or the other, rather than a mixture of both types of cart display.
