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
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