Sorry for the cryptic title, but it appears that if you set up a new print server, with the same name, and put the same printers on it as the old one using the same IP addresses, and the same printer shares, and then swap it in for the old one, Windows 7 stops printing to it.
That's right, I setup a new print server using the same host name as the old one, same IP address, added the same printers to it using the same drivers, and the same share names, but Windows told the users that the printers were unavailable.
The only way to get them working again was to remove the old printers and re-map them each computer. I did this through Group Policy, but it still took a while for it to cascade out.
What the hell Microsoft?
If I browse to http://www.microsoft.com/ one day, and the next dat a new server is put up to host http://www.microsoft.com, I wouldn't expect all of the client web browsers to break.