I had been using this site trouble free along with Sopcast on a previous laptop. Since I got a new laptop, I downloaded Sopcast as I did before (definitely have it, can open up etc). However, when I now click on a link that is P2P and with Sopcast - it doesn't automatically open my sopcast and play it like it used to. Instead, it redirects me to a page saying 'cannot be displayed' and saying I require a program to be installed etc. I remember when this first came on in the past when I was new to the site so I clicked looked for programs and knew I had to download Sopcast. However I already have it installed so can't see why it isn't working?
When you say you definitely have sopcast and can open it up can you try and click the following address and see if it opens up sopcast and plays? It's a Romanian Digisport channel and is on most of the time sop://broker.sopcast.com:3912/111686
If it does not I suspect you did not grant sopcast authority to your firewall when you installed it.
Another test if it does not open sopcast and play is for you to open sopcast manually and paste the above link into tthe sopcast address bar and then click the right arrow to load that address and see if it plays.