I was doing some importing myself, and the problem happens when the file is in ISO-8859-1 format. I saved the file again with UTF-8 encoding, and the import happened smoothly.
I didn’t go too deep, but as far as my debugging have gone, it seems that the problem is after get_posts() function in import/rss.php.
$post_content had the right value ’till after cleaning up the content.
I don’t know if this helps, but I hope it does.
Best Regards!
Renato “Lond” Cerqueira