For those having problems using SH404SEF and Joomfish 2.0.3 together, read this.

I know many people have problems when switching from one language to another. Only the active menu item is shown. The other menu items simply don't show.

Here is how I fixed it:

# Joomfish fix
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !^/index.php
RewriteCond %{REQUEST_URI} !^/en/.*
RewriteCond %{QUERY_STRING} !lang
RewriteRule ^(.*)$ /$1?lang=fr [R]

You'll need access to your .htaccess file of course. You'll also need to edit this line, depending on your URLs structure:
RewriteCond %{REQUEST_URI} !^/en/.*

If you need help fixing it, just PM.

Cheers.

Doing a bit more testing I found out that the problem doesn't have anything to do with Artio, it depends directly from the mod_mainmenu module of Joomla.

If anyone has the same problem here is a topic explaining how to solve it
Joomfish forum