CUPS printer prints garbage from VM (was: VM client can't access CUPS printer)

[Steve Kleene <skdeb@syrano.acb.uc.edu>]

I have a Wheezy host with a USB CUPS printer (Xerox Phaser 6280DN) and a
virtualbox XP client.  All of the software is up-to-date, including the vbox
guest additions and extension pack.  The VM (client) accesses the CUPS
printer but just prints a page of PostScript errors.  Here's the whole story:

1. From the host, PostScript has always printed fine, supported by
   /etc/cups/ppd/Phaser_6280DN.ppd.
2. I have a saved VM from when the Phaser had its own IP on a local hub.  I
   can still print fine from the VM with that configuration.
3. If I delete that VM printer and re-define a network printer with the IP
   of the host's CUPS printer, I can still print from the VM.  In other
   words, it succeeds in accessing the CUPS printer.  However, the printout
   just shows a few PostScript errors (from either Word or Acrobat).  I can
   post those if it might help.

I found the directory with the client's driver files and made sure all of
those files were the same before and after replacing the printer definition.
In one trial, I also deleted that whole directory before defining the new
client network printer.

So two questions:

Q1. Are the client's drivers even relevant here when it accesses the CUPS
    printer, or is everything done by the host's PPD?
Q2. Any ideas how to get printing from the client to work?

I have a similar setup that works at home but with an old HP LaserJet 5MP.

Thanks.