I installed version 1.2.4 directly and there is the same problem with the language ( Spanish ) , is unchanged. When I upgrade from version 1.2.3 to 1.2.4 work properly. 
the only way it will work in Spanish is changing it in this window (change auto for spanish) here
What language did you tried to set exactly via the amin/language.php?
When I select the Español (España) - Spanish (Spain) language via the amin/language.php, this is working as expected (see the screenshot below).
BTW: Setting up the default language via the admin/multilanguage.php page and the admin/settings.php page as the same effect: This sets the default language for new created accounts and the guests (login and lost password pages).Also, don't forget that if you switch into another account and that you set the language via the language page (profile menu) of the user into which you have switched, you'll not see any difference. You must login with that user to be able to see the interface with its language.
Quoteif I select, the Spanish in the last image works, but if this automatic language is English, but my browser chrome, ie and firefox are in Spanish, not a big deal, it was just a curiosity.
I understand nothing... Spanish or Español (España) - Spanish (Spain) ?
Ok. To resume, when you set auto, this doesn't work (you still see english).
Please, can you install firebug on your firefox and show me the Accept-Language header string from your browser when you query your panel URL?
See the screenshot below for an example: Accept-Language fr,fr-FR;q=0.8,en-US;q=0.5,en;q=0.3
I thinks that your problem is due to the fact that your browser is returning the es string at the first place (Spanish) and thus, because that language has only one string translated, you still see the English strings (when auto detection is enabled). If you want, I can explains you how to remove the related es.mo file. That should solve your problem.
firefox restore values and now works in Internet Explorer and Chrome do the same but without result.
worry not only my clients are Spanish, I change the language Spanish and deactivate the automatic, thanks
I think here auto will use Spanish instead of Español (España) - Spanish (Spain)..
And because that es.mo only contain one translated string... This lead to confusion... I could remove that es translation file which is useless here.
