How about adding 2 more replace querys, such as changing the lastposter info if any of the old account to the new account on the main forum display and in the thread listing.
Although, it is required to have the actual username and not the userid.
ie, adding the following 2 sql commands
Code:
update forum set lastposter='NewName' where lastposter='OldName'
and
Code:
update thread set lastposter='NewName' where lastposter='OldName'