DP8 Most likely, you are hiding or blocking the referrer when you are browsing (various security programs enable this for "private" browsing).
In order to download apps hosted on MacUpdate servers, they need to come from macupdate.com domain names. So if you block the referrer URL, it can't see that and loops you back. This is to prevent extreme bandwidth costs from direct outside linking.
Try disabling the referrer blocking - or contact me desktop@macupdate.com and I will be glad to help you out.