I know this sound strange, but it's exactly what is happening. We're using HelloMinty theme. When you click a product after looking at the grid view, it goes to a page that looks kind of like the magento default view (except the coloring is that of the theme) - header/footer, etc. goes away. If you add it to the cart, and then look at recently added items, and click it again - it goes to the properly themed page. I can submit examples if you E-mail me.