Contextual filter and path alias
I ran into a similar problem recently.  The issue is that internally the "Raw value from URL" doesn't get its data from the URL, it gets its data from the unaliased url.  So if you have a node with an alias like mysite.com/foo/bar, you would expect 'bar' to be the argument passed with a path component of 2.

However since foo/bar is actually node/123, internally it becomes node/123, and '123' is what gets passed to the view.

I have opened a ticket in the views issue queue (http://drupal.org/node/1658352). Hopefully it will see some light with a proper fix, as I dont believe that the expected behavior is to retrieve the unaliased path.