Okay, I found why the last thread isn't moved, here is an example:
UPDATE w3t_Posts
SET B_Board = 'website'
WHERE B_Main = '1569' OR B_Main = '35731'
AND B_Board = ''
;
The precedence of AND and OR makes it: B_Main = '1569 OR (B_Main = '35731' AND B_Board = '') which is all except the last one. I fixed it by adding parens around the WHERE $Formatted_q in the UPDATE. Of course it doen't move posts now becasue of $oldbard not being set, so on to that...
Lee