Spurious trackback and rss feed URL's from attachment URL

On 10 August I upgraded from 2.6 to 3.0.1. WP told me I needed to upgrade my DB and did it automatiically for me

After this upgrade we get (not on all posts, just some) errors of spurious trackback and rss feed URL’s created.

Here’s an example:-
XEnu’s linksleuth tool says we have a broken link http://www.peteranne.it/wp/wp-trackback.php?p=1485
error code: 404 (not found), linked from page(s):
http://www.peteranne.it/wp/?attachment_id=1485

If I go to , the link that doesn’t work is indeed there at the foot of the pgae. However, as you will see if you look at it, this link isn’t the post I made. Hover over New Rother walking guide to Sardinia recommends The Lemon House and you can click though to the post I made http://www.peteranne.it/wp/?p=1484 which works fine, including the trackback.

How can I eliminate these errors?
thanks Peter