Failing UTRLs in user digest messages

[Peter Gentry]

Whenever I click on the URL pointing to a user attachmentin a digest message I 
get the "The webpage cannot be found" message This
error (HTTP 404 Not Found) means that Internet Explorer was able to connect to 
the website, but the page you wanted was not found.
It's possible that the webpage is temporarily unavailable. Alternatively, the 
website might have changed or removed the webpage.

What have I got wrong?

I am using Outlook and IE9 with Vista Home Premium

A typical failing link is 
http://lists.gnu.org/archive/html/lilypond-user/attachments/20120907/7433053a/attachment.png

Other users web site urls in list messages work all the lists.gnu.org links fail

regards
Peter Gentry