Is your forum organised with categories?

Yes, the forum has several categories, where some of the category names are using text other than English.

IMHO the languages shouldn't make a difference. In my forum (and also here) some of the categories are named in english some other in german or different languages (but all in languages written in latin letters some with diacritics).

Please add the following codelines to includes/index.inc.php between the codelines 64 and 65 (directly before the line with mysqli_query($connid, $display_pid_result)).

echo "<pre>". print_r($connid, true) ."</pre>";
echo "<pre>". print_r($display_pid_result, true) ."</pre>";

This should display the query that seems to be broken. It will cause error messages about alredy sent headers and maybe more but it becomes visible, if the query is really broken or not.

Please copy the SQL-query and show it here in a reply. If there's some (unbroken) value, that should stay private, remove it before posting the query but best would be to show the complete query.

Thank you in advance.

Tschö, Auge