new colour printer only uses black and white

[Dave Howorth <dhoworth@mrc-lmb.cam.ac.uk>]

I'm a lucky boy! We just installed a new HP4650dn colour laserjet. 
Almost everything seems good but it is printing in monochrome from my 
Debian box (mostly!).

It's a network printer that replaces a previous one (a QMS magicolor 
2200). I use CUPS and I've added the HP. I can still print as before in 
colour to the QMS. I can print to the HP but it comes out in b&w, 
including: CUPS test page, mozilla, gvim, acroread, gv, lpr from the 
command line. BUT ... gimp prints in colour. All the other boxen in the 
room seem to have no trouble printing in colour (Suse, OS X, even W2K in 
a VMware cage)

I've looked at every control panel and dialog box I can find and 
searched the CUPS user manual but can't find the problem. If anybody has 
any clues, I would much appreciate it.

Thanks, Dave