[cups.general] number-up printing not working via lp to HP 9000 MFP

[JLM]

We recently upgraded our version of CUPS to 1.2.4. This is the stock version that comes with RHEL 5. We have HP 9000 MFPs and also the HP CLJ5500. I can no longer print 
using the lp command and giving it the -o number-up=n option and have it put multiple pages on a single sheet. This doesn't work solely with the 9000 MFP. It does work with 
the CLJ5500. Also, this does work from Windows, and from Linux applications like Evince.

We have modified our PPD file in an attempt to correct this situation, to no avail.

What's the problem here? If anyone has this working for their HP 9000 MFP and could send me the PPD that would also be quite helpful.

Thanks.