It appears that the Payment Variable Information URL you have defined in that product's settings did not respond when we attempted to POST the order details to it.
Curiously, HTTP status 302: Found usually indicates a successful redirection from the original URL to a corrected URL -- e.g., this may often be used to ensure all pages on a site are browsed with/without a "www." prefix on the domain, or to ensure that old page URLs point to those pages' new locations after a site has been substantially restructured. However, I checked the actual URL your recently-purchased products have been POSTing to, and in this case the 302: Found redirection is pointing to another URL that's 404: Not Found (or maybe this redirection is just your host's way of handling not-found URLs in general), hence the error notification. We'd recommend examining that product's Payment Variable Information URL setting very closely to make sure it's correct and accurate.
I notice you are also using the Common Notification URL (defined in Seller Admin > Account Preferences) to POST full order data to a URL for every sale, which differs from the URL you'd defined in the affected products' settings, so I'm wondering if that URL might be a newer setting intended to replace product-specific URLs, or vice-versa, and you simply haven't deleted the obsolete URL settings yet?
Bear in mind that we would submit separate POSTs of the full order data to your Common Notification URL and to each Payment Variable Information URL you'd defined for individual items in that order, though the latter can include a few variables not sent to the Common URL, as we document in detail under the "Item Specific Non-IPN Data" section here:
If you're still not quite sure what's going on and wish to provide us with more specific details that you'd rather not post publicly here, feel free to email us directly: