I've been using torrents for a few years now, and have never had this problem. Suddenly every torrent I try and download can't find sources, no matter how many seeds there are. I even had one with over 1,000, and still it wouldn't find sources to download. It doesn't start at all.
It can't be a firewall issue, because as I said, I've never had this problem. It MIGHT be that I've just recently switched from Limewire to Frostwire, but in the few months I've had it, it's also worked fine with torrents.
I have always been using the site edited by ddp I guess it is the only web site that offers free adult movie torrents and guarantees virus-free environment!