process printing doesn't stop

[marko.melix at fatwebnet.it]

I have installed Red Hat 9.0 and related cups system , to configure cups I used Printer Administration section in Webmin and I have set an Intel print server as Remote Unix Server:
IP_ADDRESS - COM1_PASSTHRU - BSD
this print server is link to a plotter (very old HP Draftmaster) and when any user print out to samba share plotter it start to print but it never stop and continue to replace the same drawing.
With "ps -aux" I can see the process always running.
I have others printers configured as IP_ADDRESS - PORT (9100) on the same server and they works fine.
Samba is linked to cups library and /var/spool/samba is clean.
Is it probably a right permission problems on /var/spools/cups directory? The cups user and group are the default lp/sys, or it depend by the samba client that send the job maybe nobody?
Can you explain what's happen?
Thanks.