WordPress MU

I have just installed wpmu 1.2.3, it's ok, but the translation don't work. I created the folder wp-includes/languages/ and here i put the .mo files. When i go to Site Admin >> Options, I can choose my prefered language, and also in Options >> General. But it has no effect. Also I tried to add the iso code at wp-confing.php
define('WPLANG', 'ast_ES');
but i only see the english version.
Also i created languages/ folder into wp-content

I don't find any solution about that on the forums...

Note: on wpmu 1.0 it works

Works in 1.2.3 for me. What specific language are you adding in?

Can you please verify that the file name in question is ast_ES.mo?

Where did you get the translations files from? Please provide a URL.

I use two language files es_ES.mo (spanish) and ast_ES.mo (asturian) the first one i found on the forums the second one it's made by me.

The same files works on 1.0 but not on 1.2.3