Cressida 
you were lucky, you did not leave a pointer to this thread in the
davey topic you have referred to this would have alerted me, it was by accident that I saw your topic. Anyway connection made again.
[james@localhost ~]$ lpstat -t
scheduler is running < ---- means cups is running
system default destination: Hewlett-Packard-HP-LaserJet-6MP < ------ I am impressed you have set default
device for Hewlett-Packard-HP-LaserJet-6MP: hp:/par/HP_LaserJet_6MP?device=/dev/parport0 < --- using parallelport
Hewlett-Packard-HP-LaserJet-6MP accepting requests since Mon 23 Jan 2012 08:42:05 AM CST
printer Hewlett-Packard-HP-LaserJet-6MP is idle. enabled since Mon 23 Jan 2012 08:42:05 AM CST
ready to print
Hewlett-Packard-HP-LaserJet-6MP-171 donna 34816 Wed 18 Jan 2012 12:51:40 PM CST
Hewlett-Packard-HP-LaserJet-6MP-172 donna 34816 Wed 18 Jan 2012 12:57:30 PM CST
[james@localhost ~]$
Hewlett-Packard-HP-LaserJet-6MP < ---- your particular
printer que name or
printer name, notice this differs from the one you had used in the link you refer to. This is why instead of trying to get people to describe/type I ask for the result of
lpstat -t and at the same time some valuable extra information is gained. The CUPS server is running, your connection type plus some que management in the form of a couple of jobs. All fine.
[james@localhost ~]$ lpoptions -p Hewlett-Packard-HP-LaserJet-6MP
auth-info-required=none
copies=1
device-uri=hp:/par/HP_LaserJet_6MP?device=/dev/parport0
finishings=3
job-hold-until=no-hold
job-priority=50
job-sheets=none,none
marker-change-time=0
number-up=1
printer-commands=none
printer-info='Hewlett-Packard HP LaserJet 6MP'
printer-is-accepting-jobs=true
printer-is-shared=true
printer-location=localhost.localdomain
printer-make-and-model='HP LaserJet 6mp pcl3, hpcups 3.alot' < --------- Here is this odd version again
printer-state=3
printer-state-change-time=1327329725
printer-state-reasons=none
printer-type=167964
printer-uri-supported=ipp://localhost:631/printers/Hewlett-Packard-HP-LaserJet-6MP
In above I have highlighted what interests me most, but mainly it is the driver I look for here
3.alot I do not understand what is going on here, I don't think it is a error on your part. Can you just check in CUPS Web access, the line should be something like
printer-make-and-model='HPLaserJet 6mp cups pcl3, 3. 11. 10'I can only get it to show right here in Forum by adding a space after the 3. and 11. as above line. I now suspect this indicates the wrong driver for the printer but not quite proved yet.
[james@localhost ~]$ lpoptions -p Hewlett-Packard-HP-LaserJet-6MP -l
PageSize/Media Size: Card3x5 Hagaki Photo4x6 A6 Photo5x7 Card5x8 Oufuku A5 B5 JB5 Executive 16k *Letter A4 ExecutiveJIS FLSA Legal EnvA2 EnvC6 EnvChou4 EnvMonarch EnvDL Env10 EnvChou3 EnvC5 EnvB5 Custom.WIDTHxHEIGHT
Duplex/Double-Sided Printing: DuplexNoTumble DuplexTumble *None
InputSlot/Media Source: *Auto PhotoTray Upper Lower Envelope LargeCapacity Manual MPTray
ColorModel/Output Mode: *Gray
MediaType/Media Type: *Plain
OutputMode/Print Quality: *Normal Draft Best
OptionDuplex/Duplexer Installed: False *True
[james@localhost ~]$
This is powerful information when you are trouble shooting, the above is a correct profile (note I did not say it is correct for your printer) this information is is correct for a printer. It may in fact be fine as mini profile, but I doubt this profile unleashes all the power.
I would recommend you install another printer que using CUPS and use the printer driver
Edit: have changed to simplified versionprinter-make-and-model='HP LaserJet 6MP - CUPS+Gutenprint v5.2.7 Simplified'In case you don know how to use CUPS Web interface try to click on this
http://localhost:631 then
Administration > Add Printer > Probably asked for root/<your system password> > Follow directionThe main thing, I would like you to try another driver because in my opinion something seems to want to install the wrong driver for 6MP (notice the driver is listed with lower case 6mp, this fooled me for a while in the davey topic

)
I am not clear on how exactly you have installed the driver but at a guess via HP interface or PCCC (have tried this in the past and it became hit and miss, when I found that I was getting very consistent results using CUPS I never looked back.)
When you have installed the recommended printer driver above your 6MP installation should show:
(changed to reflect the simplified version above, ie if you happened to see before I edited)
[gert@localhost ~]$ lpoptions -p test -l
PageSize/Media Size: A4 *Letter Legal Executive Statement
ColorModel/Color Model: *Gray Black
InputSlot/Media Source: *Standard ManualAdj Manual MultiPurposeAdj MultiPurpose UpperAdj Upper LowerAdj Lower LargeCapacityAdj LargeCapacity
StpQuality/Print Quality: None Draft *Standard High
Resolution/Resolution: 301x300dpi 150dpi 300dpi *600dpi
Duplex/2-Sided Printing: *None DuplexNoTumble DuplexTumble
StpiShrinkOutput/Shrink Page If Necessary to Fit Borders: *Shrink Crop Expand
StpColorCorrection/Color Correction: *None Accurate Bright Hue Uncorrected Desaturated Threshold Density Raw Predithered
StpBrightness/Brightness: 0 100 200 300 400 500 600 700 800 900 *None 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 Custom.REAL
StpContrast/Contrast: 0 100 200 300 400 500 600 700 800 900 *None 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500 2600 2700 2800 2900 3000 3100 3200 3300 3400 3500 3600 3700 3800 3900 4000 Custom.REAL
StpImageType/Image Type: None Text Graphics *TextGraphics Photo LineArt
[gert@localhost ~]$
Ah yes, if you know how to use the html tags, to place
code or
quote in posts it does ease it on the brain.

I just picked this driver at random as I am short of time. So you will be helping out proving something.