hi Qukler..
it's possibly because there's a mismatch between your database tables.. make sure your database collation is utf_unicode_ci and all of your tables are same too...

to get the best result, make a brand new installation and follow these steps:

1.Create a brand new database.
2.Set it's collation to "utf_unicode_ci".
3.Open up your .../conf/locales.php before the installation and make these changes:

$force_io_charset_if_accepted = 'utf-8'
$db_config['connection_charset'] = 'utf8'

4.Now you are ready to begin the install, make the installation.
5.After the install check every table and subtable is set to utf_unicode_ci, they all have to be same now (utf_unicode_ci) and everything should work out well
if not; change all the tables accordingly.

There are two kind of issues i have met.. even if you have everything converted to utf_unicode_ci after getting those ??? or unknown characters, it wont bring them back as they were already converted to other characters..

Secondly, even if you have everything set properly you might have problems with the formatting.php, but that shouldnt bother you if you use Spanish (utf8) or whatever that lang is (: using latin5_... etc windows version of the charsets may cause problems.. make sure you are using the utf8 version of your lang.. what is ur default locale?