All (almost all. the charset is a mess now, on my Portuguese forum) is working fine and no problems.
Since UBB.threads 7.5.9, the default character set has been updated to use the standard UTF-8. Since you've upgraded from an extremely old version of UBB.threads, you may have been using iso-8859-1 character set. This normally has little effect on English speaking forums, but since your forums are primarily Portuguese, you'd be better to switch the character set back to "iso-8859-1" -- I believe this is what you were previously using (?)
The correction is easy to perform.
1. Go to: Control Panel » Languages
2. Click on the "Language Editor" tab.
3. In the "Search String" field, type "UTF-8" and press "Go" button.
4. There may be one or two items that are shown. "myfeeds.php" and/or "generic.php" -- Click "Edit" next to "generic.php"
5. At the very top, you will see "CHARSET" highlighted in RED. Replace "UTF-8" with "ISO-8859-1" -- !!do not add any spaces or line-feed before/after this text!!
6. Scroll to the bottom and click on the "Update Language File" button. It does not matter which of the two buttons you click on, they both do the same thing.
Done.OR -- If you would rather edit the language file directly:
IN /languages/english/generic,php
FIND:$ubbt_lang['CHARSET'] = "UTF-8";
REPLACE WITH:$ubbt_lang['CHARSET'] = "iso-8859-1";
