This looks like the columns being searched are int vs char.
ubbt_FORUMS FORUM_ID is
int(9)ubbt_FORUM_PERMISSIONS FORUM_ID is
varchar(100)If you turn off SQL strict mode, the error you have now should turn into just a warning, and you will be able to proceed.
But i believe this may be easily fixed at the code level by just adding single quotes around the string.
Give this a shot
FIND IN admin/dodeleteforum.php AROUND LINE 35
delete from {$config['TABLE_PREFIX']}FORUM_PERMISSIONS
where FORUM_ID = ?
REPLACE WITH
delete from {$config['TABLE_PREFIX']}FORUM_PERMISSIONS
where FORUM_ID = '?'