Note: please be advised that with each passing month a new folder is created within the /uploads folder, according to the month you are in, and it may be automatically created with the wrong permission. WordPress Codex description: http://codex.wordpress.org/Changing_File_Permissions http://wordpress.org/support/topic/permissionsimage-uploads-1 http://stackoverflow.com/questions/18352682/correct-file-permissions-for-wordpress http://wordpress.org/support/topic/directory-and-file-permissions For older versions: http://wordpress.org/support/topic/image-upload-unable-to-create-directory-777-does-not-work?replies=6
2) importer problems
Note: the WP importer (for demo content) is a rather old (and in some ways outdated) plug-in, so it will not always perform as expected.
Any issues you may encounter are in no way linked to the theme. See http://wordpress.org/support/topic/does-not-import-images-file-attachements for information on how to deal with failed file imports. (additional link: http://wordpress.org/support/topic/import-fails-to-import-photos-attachments)