Comment 3 for bug 775668

This is because the URI is retrieved from the http://changelogs.ubuntu.com/meta-release site, it's the URI from the next versions ReleaseNotes section. Maybe the button should point to the URI from the ReleaseNotesHtml section, which is the HTML rendered version of the wiki content (in this case it's a valid update-manager bug) or the link in the ReleaseNotesHtml section should be http://www.ubuntu.com/getubuntu/releasenotes?os=ubuntu&ver=11.04&lang=en as Jean-Baptiste has mentioned, but in that case it's not an update-manager bug, but a bug to be fixed on the changelogs.ubuntu.com, so the task should be reassigned to another package.
---
Ubuntu Bug Squad volunteer triager
http://wiki.ubuntu.com/BugSquad