samba - Aug 2005 - Samba/CUPS printer queue troubleshooting guide (XP clients)?

We have a printing reliability problem with Samba printers/queues and
we are trying to figure out how to troubleshoot it more methodically.

Situation: We've been running Samba 3.x (always current/latest) for
over a year with primarily Windows 2000 clients.  This summer we are
converting our 100 Win2K PCs to XP; this conversion is nearly
complete.

Our Samba printing is CUPS-based to HP Laserjets (4000-4200 series)
with CUPS queuses configured to address the HPs as LPD queues. 
Printing-related snips from SMB.CONF are as follows:

printcap name = cups
printing = cups
[print$]
   comment = Printer Drivers
   path = /etc/samba/drivers
   browseable = yes
   guest ok = yes
   read only = yes
   write list = root
   create mask = 0775
[printers]
   comment = All Printers
   path = /var/spool/samba
   browseable = yes
   public = yes
   writable = no
   printable = yes
   printer admin = root

We realized that we needed to push updated, XP-capable drivers for
some of our 8-9 printers/queues (we did this via the Windows Print
Properties dialogues as Windows root).

Overall, printing is working.  However, we have had more occasions
where printing stalls in the queue -- we get a phone call, look in a
Windows print queue and see 2-3 docs stuck, going nowhere.  In several
cases we could not (as root) delete these and the ultimate maneuver to
clear the queue was:

 1) shutdown samba 
 2) move/delete the /var/lib/samba/printing/printername.tdb file for that queue 
 3) restart samba

This doesn't seem like the best solution :)

We rescently upgraded firmware+memory on several of the HPs to resolve
problems printing some PDFs, but documents now getting stuck are of
all types (DOC, PDF, XLS) and of all sizes -- from 1 to 40 pages.

What I am looking for are some diagnostic steps we can take to see
where the trouble lies -- is it Windows clients not releasing print
jobs to Samba?  Is it problems with spooling in CUPS? (we are at CUPS
1.1.22).

Any pointers to a FAQ or troubleshooting guide appreciated (or any
other observations!)

Thanks,

Jim