Ticket URL

Why is it that sometimes when you click on a ticket URL in the email
message, the ticket is not displayed? Infact RT responds by saying
"Ticket couldn’t be loaded ".
Subsequent to this, if you type in the ticket id and click on goto
ticket, the ticket will be displayed, and if you go back to the
email message and click on the URL again, the ticket also shows up.
What is going on here?

(RT 1.3.70)

Mixo