I doubt this has to do with your router. If you look at the reasons stated, it most likely has to do with the browser you are using, if you're not using a download manager or a non-official site. I had the same problem today, and edited my settings in Opera and ZoneAlarm for the Suprnova site. I allowed for http referrals in the Privacy settings, and after that the link worked.
Now, if only people would actually dedicate some bandwidth for uploads, bittorrent would be much better...
GL