Since upgrading to CiviCRM 4.6.9 on Drupal 6.37, when using track click throughs in CiviMail, links send to Page Not Found.
What is the url to track that generates the page not found?
One common problem is that your apache/nginx rules are wrongly redirecting the url used to track the clicks to be handled by drupal
Is this a "real" 404 page (coming from your webserver) or is this drupal handling that page and generating a page not found?
I thought this patch fixed the problem: https://issues.civicrm.org/jira/browse/CRM-7400
But, I spoke too soon. Still having the same "Page Not Found" issue when Tracking Click Throughs is turned on.