Pingback and port 80

Yes, it is. The trackback is an outbound connection on port 80. I would see if they could allow it for your account.

Um, 2.0.4? You do know that there are much newer versions, right?

Ok – thanks – yeah I did know about version – but my hosting company https://www.heartinternet has a one-click install version which happens to be 2.0.4!

Okay, this seems to be a problem with all Heart Internet Shared Hosting Servers – I too am getting the same problem.
For more information please read my blog article here:
https://www.sprayfly.com/2008/02/21/heart-internet-web-hosting-wordpress-trackbacks-and-pingbacks-not-supported/
What a headache this is causing me!