[Samba] Need help debugging the printer related "Access denied, unable to connect" message

[taso]

1. The printers are Samba/CUPS.

2. Clients are Windows XP Pro & 2000 Workstations.

3. "Access denied, unable to connect" appears in the printers window
     on the clients - nearly always. Very occasionally, it displays
     what it's supposed to.

4. Seems to be a cosmetic problem since it does not affect actual printing.

5. Can some guru advise what level of debugging to enable and where in order
    to  find out why this is happening?