I still cannot upgrade, also it will not keep me logged into JRiver Interact, When I first open the form.
That last one is a strange one. I assume you are selecting the option to stay logged on all the time? Still, it shouldn't log you out.
First on the direct download, are you able to download the file onto you PC okay, before you run it? Try
http://files.jriver.com/mediacenter/channels/v20/latest/MediaCenter200108.exe If so, and you right click the file, select properties, is the file shown as Blocked? If so, click the Unblock button and run the exe. It should now work.
If that isn't the issue, but you are able to download the file directly, then it sounds like your virus scanner doesn't like MC. If so, temporarily disable your virus scanner and install MC. If that works you will need to let the virus scanner author know that MC isn't a virus, so future upgrades will work. You can't just white list the update exe as the name changes every time.
If you can't download the MC upgrade file, then it does sound like your ISP is filtering for some reason, or has a virus scanner service running which block the download, or something is broken either at their end or yours.
As they say their end is all good, take a good look at your end.
Are you using your new ISP's DNS servers? If not they may block downloads.
Are you using a VPN? If so try without the VPN active.
Are you using all the recommended settings from your new ISP?
If you can't find anything, test to see if you can do updates for something else that should always work, like Windows or Adobe Acrobat. If those updates don't work, I think you need to make another call to your ISP, with these examples of failed downloads.