SBS 2008 Server - Install x86 printer drivers

Although this was applicable to your servers and Vista, believe the driver issue you are seeing may be the same as here:
You are prompted to install a new printer driver in Windows Vista when you try to print to a Windows Server 2008-based print server or to a Windows Server 2003-based print server
http://support.microsoft.com/kb/946225

Some other ideas here - You need to enable the Guest account on the server, by default it is disabled - source for more:  http://social.technet.microsoft.com/Forums/en-US/winserverprint/thread/91420965-7fd8-4ce0-9e07-0e3eb2360c7a

About drivers here - http://social.technet.microsoft.com/Forums/en-US/winserverprint/thread/dfa52fe9-f435-4e7a-b745-38c5c680fd59/

You cannot install third-party printer drivers for cross-architecture support in Windows Vista or in Windows Server 2008 - source for more http://support.microsoft.com/kb/952065

First, on your 2008 server, stop sharing the faxclient folder.  It is not for XP computers and it has nothing to do with sending faxes from XP.  If you unshare it, you will not be tempted to use the files inside that folder.  They will not help you.  
Second, on your 2008 server, change the fax service to use the local system account.  It defaults to the Network Service account.  I am willing to bet this one step solves 90% of the peoples problems. Restart the service after making the change.
If your XP clients are not at least SP2, stop reading this now and go update them. and source for more, if this sounds similar to your issue:  http://social.technet.microsoft.com/Forums/en-US/winserverprint/thread/e6bb99cb-254c-4f48-aaa9-7526b5fac480

Applying Deployed Printer Connections Policy.... Server 2008 - http://social.technet.microsoft.com/Forums/en-US/winserverprint/thread/add68b4a-7642-4604-a50e-650f95bdd08c/

Hope to help some with these links and synopses.  If not your solutions, hopefully others, better versed in this will step in with the perfect solution for you.  Good luck.  ":0)  Asta

So, here's how I load x64 drivers on a Win2008 SBS server and then add the x86 drivers for the client:

1. Download the x64 drivers for the printer.  Install the printer as a local printer on the print server using the x64 drivers.  Verify test pages print.
2. Download teh x86 drivers - same exact driver but for different OS - so don't download the PCL 6 x64 driver and the PCL 5 x86 driver - make sure they're both the exact same one.
3.  Then, on your print server (x64 machine), go to Printers -> Properties of your printer.  Click on Sharing and the Additional Drivers button.
4.  Check the box for x86 - likely it's unchecked and says "NO" for installed.  If so, it'll prompt for the x86 drivers, point it to the right spot.  It'll install the drivers for the x86 clients.

You're done if the above all goes well.  Verify that the "Additional Drivers" button shows YES under Installed for both drivers.

Go to your client, add the printer like normal and it should automatically download the correct x86 driver from the server - or in the case of Vista x64, it will know to grab the 64-bit driver.

Hope this helps.  Also, not sure the status of the workstation you've been working with, but follow the above directions and try adding the printer on a different workstation if you have trouble, could have driver mismatch issues on the PC you're working on.