[CentOS] CUPS not rendering documents via Samba

Hi guys, any CUPS / Samba experts out there?

The CUPS printing guide is a horrendous maze of options. I've got
nearly there but I've got
one thing wrong and I don't know where to look.

I set up our two printers (HP K5400s) using the GUI printer tool. Both
print the test page just fine.
I set up the [printers] and [print$] shares and can browse to the
printers from Windows (XP for me)
I managed to get the postscript drivers installed with cupsaddsmb and
it installs on the XP client just fine.

..... sadly it just prints the postscript instead of rendering it. I
guess the printer queue is in raw mode
but I can't see where to change it. I vaguely remember foomatic and
such from ages back. Can someone
point me at the right part of the setup to fix this please?

-- 
Kevin Thorpe
Head of IT
PI Benchmark