Joomla-SMF bridge can't handle multilanguage posts, but SMF-standalone yes

[cbpm]

I have a site with Joomla- SMF bridge. Both languages  (in joomla and SMF language files) are set to "charset=iso-8859-1". When i access the forum via Jooma-smf bridge, i can't write japanese characters, for example.  But, when i access via /forum directory (outside joomla), SMF can handle perfectly many foreign languages simultaneously, showing all correctly, as in this topic:
http://www.simplemachines.org/community/index.php?topic=6051.msg140417

I think it's a problem with both javascripts (joomla and SMF), maybe there is a conflict between both.
For example, writing a message in english and pressing the button "preview message", the preview is shown correctly.
But, if i write a sentence in japanese, chinese, etc. pressing that button, the preview is not shown. Saving the message,  instead receiving characters as:

Code Select Expand

عن محركات
i only get garbage ascii characters.

Outside Joomla,  running alone the forum,  all is working good. 

Any ideas?

I'm using Joomla 1.0 and SMF 1.1 Beta 3 Public with bridge.