That's good, so the only problem remaining now is the attachments. These are all stored in the article_attachment table as longblob. As I'm typing this I'm actually remembering something about blobs being excluded from conversion operations, because they are not stored in any particular charset (they are raw binary, you can view them using a specific charset, but they are not stored conforming to any charset):
http://dev.mysql.com/doc/refman/5.0/en/blob.html
So if you have ran a charset conversation operation on them such as iconv, then you may have rendered them unreadable. I think the solution was to do the reverse conversion on them to restore them to their original format, so in this case from UTF8 to iso~ or latin1.
You could try to run an ALTER TABLE statement to see if this does the trick, or failing that, dump the article_attachment table on its own, convert it back, and then re-import it. There is also a longblob column in the article_plain table that you may have to do this with as well.
If the data itself has been truncated by the conversion process, where a too-large value couldn't be inserted, then you may have to restore the article_attachment table from a backup of the database instead.