Simonnicol,
I looked at your post and I'm not sure if you figured out the problem or not. I've looked at an Artisteer theme before and the code they generate is kind of messy for my tastes but if they work for you that's ok.
The problem with themes is when they don't have a unique id for each post. If you look at the code in index.php, single.php, and page.php of the default theme each post is wrapped in a div something like:
<div <?php post_class() ?> id="post-<?php the_ID(); ?>">
This results in code like:
<div class="post-147 post hentry category-site-news category-studies-works-in-progress tag-galleries tag-sketches tag-studies" id="post-147">
with the important part being id="post-147". Without this, the translate plugin doesn't know what portion of the page to translate.
So if you're comfortable editing php code yourself it isn't too hard to fix most themes. Otherwise you can upload the files somewhere and I can tell you how to fix them.
(The next version of the plugin will have a partial fix for this.)