When trying to edit a complex language like Spanish, Arabic, Turkish, got some errors :

[phpBB Debug] PHP Notice: in file /includes/acp/acp_language.php on line 1272: htmlspecialchars() [function.htmlspecialchars]: Invalid multibyte sequence in argument

I fix it doing this :

#

#---- [ OPEN ] ----

#

root//includes/acp/acp_language.php

#

#--- [ FIND ] ----

#

function add_input_field()

#

#--- [ FIND ] ----

#

$value			= array_shift($keys);

#

#---- [ REPLACE WITH ] ----

#

$value			= utf8_normalize_nfc( array_shift($keys) );

After this I'm able to edit the language, and found some invalid charactes

And some times, ( this should be a translator problem by duplicated variables ) :

[phpBB Debug] PHP Notice: in file /language/tr/common.php on line 47: Constant TR_LANG_VERSION already defined

No clue how to fix it

Tested on 3.0.5 RC1, fresh install, no mods