Reboot the printer or login as a different user?
If it can't find the new users in an LDAP environment but can find the people from before, I would assume the new users are not within the same Search directory Root.
it gets addresses from the Exchange server. how can I force an update?
The Address book has its own section in CWIS, and that is where you add users.
on a few printers, there are some missing emails when doing a Network Address Book Search. is it possible to manually update the Address book?