I am having trouble with my standard PayPal integration. I am using basic PayPal 'Add to Cart' form buttons on my site (link). I have been using this for a while now and haven't seemed to be having any issues except occasionally I'll get an email about people having trouble adding multiple items into the PayPal cart. I just tested this and can reproduce the issue. Adding the first item into the cart works as expected. (Test by adding this item first). Once the PayPal popup window shows up, I hit "Keep Shopping" which brings you back to my store as expected. The problem is when you add a second item to the cart (try this one - or any others). It just brings you to the PayPal login page and even after logging in to a PayPal account, it doesn't show the cart... everything seems to be lost. Any ideas?
I think I found the problem. Looks like MS Frontpage was messing with the forms for the paypal buttons on some of the products. I think I fixed them. It wasn't all of them which is why the ones I included in my OP worked. Thanks for testing Avitus.