Lines missing from a printed ps file

[Eddy]

Hello,

I need some help with the following problem.

I've got this ps file http://users.belgacom.net/ef/essai10.ps (43k) that
I can't print properly on my system
	Debian Sarge with cups 1.1.20final+rc1-10
	HP Deskjet 6122 with hpijs
	file sent directly to cups using the lp command or via xpp
What happens is that horizontal lines in the second equation are not
printed, some numbers are only partly printed.

Well I tried printing this same file on the same machine using Knoppix
3.3 and all went perfectly well.

I think the same softwares were used and I suppose the only differences
were their versions and / or their configurations.  Therefore, I see two
possibilities :
  - a bug somewhere (unlikely I think, the problem has existed for
months now and I've been upgrading Debian several times since; yet I
know other people using Sarge with a HP Deskjet who have the same problem);
  - I need to change the configuration.

Playing with the printer config in xpp doesn't change anything.
I don't know how to tweak Cups or Foomatic or ...

I set LogLevel to debug but I don't know what to do next.
Here's part of the log under Debian
http://users.belgacom.net/ef/debian-error_log-stripped (11k)
and the one from Knoppix
http://users.belgacom.net/ef/knoppix-error_log-stripped
(14k).  I removed the dates from the beginning of lines to make a diff
comparision easier and also replaced "[Job 566]" by "[Job #]" for the
same reason.

If I can see for myself the differences, I don't know enough to find out
which ones are significant and what to do next.

Could anyone share their knowledge and have a look at those logs and
suggest what to do.

Thanks a lot.

-- 
Eddy
          "La notion de passoire est indépendante de la notion de trou."
		                                 Les Shadoks