[CentOS] Can't connect to torrent tracker

Well, yesterday my 5.1 and 4.6 systems could connect to

  torrent.centos.org

OK. Today neither system can connect. I can ping, but that's all. No
changes were made to the firewall during this time.

Any tips on debugging this?

I successfully http downloaded all the ISO images from various mirrors
this morning, so I think my net and firewall are OK.

TIA
-- 
Bill