I'm not sure when this broke, as I was just alerted to it. Running Drupal 7 and CiviCRM 4.7.6.
Events receive differently structured URLs in Manage Events and Events Dashboard.
Manage Events shows a URL like http://www.mydomain.com/civicrm/event/info?id=66&reset=1
Event Dashboard shows a URL like http://www.mydomain.com/civicrm/event/info?reset=1&id=66
Both URLs work and take you to the event page. However, if you embed the Dashboard URL into a mailing with link tracking enabled, the link will not redirect properly. You receive the error below:
Sorry but we are not able to provide this at the moment. Could not find valid value for id
Return to home page.
So, depending on how you navigated to the event page to obtain the URL, the link may or may not work when embedded into the mailings.
I'm not sure if there is a reason behind the differing formats for the two pages and it needs to be that way or if the resolution is in the redirection.