I've just set up a CentOS 6.5 64-bit VM with CUPS (1.4.2) and Samba (3.6.9) and can print from my Windows 7 64-bit machine quite happily.
The shared printer is a Kyocera FS-2100DN, for which I downloaded a PPD file from the Kyocera website, and I was able to use the Kyocera universal KX driver set version 611118 to add the shared printer to my own machine, but when I use the Server Properties dialogue from Windows, I can't upload drivers to the print$ share so that others can add the printer using point and print.
I've checked, and I can create/upload files to the print$ share, and I've temporarily turned off SELinux to test this.
The error, though, is:
The folder you specified doesn't contain a compatible software driver for your device
This driver was exactly what I used to install the printer (shared from the Samba machine) on my own PC, so it definitely is a driver for the printer.
Where can I go from here to get the x86 and x64 drivers onto the Samba server?