It surprises me when I kept failing importing content from WordPress.com to self-hosted WordPress installation.The error messages were:
Failed to import
and
Invalid post type
Fortunately, a simple google search solves this. The link to WordPress Forums above describes a “hack” on how to import content from WordPress.com to self-hosted WordPress installation.
Hint: compress it into .gz first, then import it. It is quite weird but it works.