I wanted a very simple cart and spent the last few hours setting it up and I was happy with the results. Upon testing, I found that when I get as far as paypal and then CANCEL the order, the return link displays my paypal password in the url as if it were a page... I uninstalled very quickly. Please test your own.
I would have liked to know about that and be of some guidance to you. I haven't seen you on the very active forum with this issue. However, I do not think this is a SimpleCaddy issue as the return url is issued by PayPal, not by SimpleCaddy... Please check your PayPal settings!