There's the issue.
32-bit printer drivers don't migrate well (or more often, at all) to Windows 64-bit editions due to the changes in the way the kernel interacts with printers. Further, I've found HP printers using HP printing ports (as opposed to standard TCP/IP ports) won't migrate at all even if they are supported.
For each printer on the Windows 2003 server, see if there's a Windows 2008 compatible driver update; it may help in the migration. Otherwise, you're sadly in the boat of re-created them by hand.