Here's a common problem with aliases:

• users/[user:name]/blog -- This is a page defined by Panels. It shows a list of latest blog posts
• users/[user:name]/blog/[node:title] -- This is the alias of the node that is a blog post. But if you will try to use it, Drupal thinks you refer to the Panels page, and shows you the lastest blog posts, instead of the node

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