[Mystics]

Do you have more than one plugin using the hook newpost_process? The prefix plugin should contain this code:

if ($type == 'thread')
{
	$dataman->setr('threadprefix', htmlspecialchars_uni($post['threadprefix']));
}
global $global_threadprefix;
$global_threadprefix = $threadinfo['threadprefix'];

Try to replace "setr" with "set".

Or try to replace the whole plugin code with this:

if ($type == 'thread')
{
	$postthreadprefix = htmlspecialchars_uni($post['threadprefix']);
	$dataman->setr('threadprefix', $postthreadprefix);
}
global $global_threadprefix;
$global_threadprefix = $threadinfo['threadprefix'];