Problem with my printer and cups

[Francois Fayard <fayard@clipper.ens.fr>]

Hi,
I've got a problem installing the printer of a friend on his plain woody.
He's got a HP Deskjet 640C : this means a non posscript printer

I've configured CUPS through the web interface after installing the
package that contains all the PPD files.
first :
 - the printer prints when I do a : echo "hello wold" > /dev/lp0
 - the printer doesn't print a test page (but it used to. Don't know why)
 - When I do a lpr -Pdeskjet file.ps it just says lpr : deskjet unknown
   printer

I don't understand what the hell it going on.
Thanks for your advice

Francois
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