Soem Panasonic Printer/Copiers (mine is a DP8060) seem to have trouble with PCL5 and PCL6 drivers. The have their own driver that I've used successfully on a Windows 2008 x64 print server which is servicing XP Pro x32 clients.
See if you can install one of their GDI drivers, instead of PCL. After I did that all the clients worked.