CUPS permissions

[Charles Trois]

I cannot get printing done on my Epson 740: when I ask for a job, it is said
to be transmitted to the printer, and it appears on the list of terminated
jobs, but nothing gets done.

So I ran cupsd in the debug mode, and this is what I got in
/var/log/cups/error_log after an attempt to print:

I [04/Dec/2003:16:13:04 +0100] Job 37 queued on 'epson' by 'root'.
I [04/Dec/2003:16:13:04 +0100] Started filter /usr/lib/cups/filter/pstops
(PID 2790) for job 37.
I [04/Dec/2003:16:13:05 +0100] Started filter
/usr/lib/cups/filter/cupsomatic (PID 2792) for job 37.
I [04/Dec/2003:16:13:05 +0100] Started backend /usr/lib/cups/backend/usb
(PID 2793) for job 37.
I [04/Dec/2003:16:13:05 +0100] Started backend /usr/lib/cups/backend/usb
(PID 2793) for job 37.
E [04/Dec/2003:16:13:05 +0100] PID 2790 stopped with status 1!
I [04/Dec/2003:16:13:05 +0100] Hint: Try setting the LogLevel to "debug" to
find out more.
E [04/Dec/2003:16:13:05 +0100] [Job 37] unable to open print file
"/var/spool/cups/d00037-001" - Permission denied

Can someone help me to understand? In /var/spool/cups, there is no file
d00037-01, only a file c00037 (perhaps related, but how?).

The problem is to find that d00037-01 file, and to know what permissions
should be given. 

I shall be grateful for all suggestions.

Charles