[Samba] Cups + Samba : Unable to get jobs for ipp://localhost/printers/prntest

[HM]

Hello all !

I encouter problems with samba / cups for printing from client machines 
of the domain.

samba : 2.2.8a-0.1
cupsys : 1.1.20final-12.backports.org.1
clients : w2k sp4

The problem is extremely strange : when i log in on a client machine of 
the samba domain, and try to print, Windows refuses and i get an error 
message. I can then see in syslog the line :

   Unable to get jobs for ipp://localhost/printers/hp - 
client-error-not-authorized

I saw on the cups website that this error could be related to the 
version of cups, and i decided to upgrade to the backports version. But 
this hasn't changed anything, since the problem persists !
When i set the smb.conf option "printcap name = cups", i get the error 
and the line in syslog. But if i "rem" this option with '#', i don't get 
this message. Windows tells me that printing if ok, but it isn't and i 
don't see any message about a printing spool in the logs.
Something interesting too : command line printing always works (a2ps / 
lpr always works). And printing from another XP machine (not in the 
domain, only in the workgroup) works too...

I'm completely lost !!!

If anyone has a clue before i spool my printers by the windows of my 
room.... ;-)

Thanks in advance !