"Printer not connected; will retry in 30 seconds..." - Samsung ML-2550 on Debian 4.0

[Dave Page]

Using Debian 4.0 with kernel 2.6.18 and CUPS 1.2.7, I try to set up my USB Samsung ML-2550 mono duplex laser printer through the CUPS web interface.

I'm starting from scratch here and deleting any printer config I may previously have had, to document my steps.

I click "Add Printer", give it the name "Samsung", a location and description. For the device, I select the USB device "Samsung ML-2550 USB #1 (Samsung ML-2550" from the drop-down list. For the driver, I provide the recommended Postscript PPD which I downloaded from http://www.linuxprinting.org/show_printer.cgi?recnum=Samsung-ML-2550

I can then look at http://localhost:631/printers/Samsung which shows me:

 Samsung
  Description: Samsung ML-2550 Mono Duplex Laser
  Location: Next to Tandoor
  Make and Model: Samsung ML-2550 Foomatic/Postscript (recommended)
  Printer State: idle, accepting jobs, published.
  Device URI: usb://Samsung/ML-2550

So far, so good. I go to "Set Printer Options", and set the paper size to A4 and the error policy to "abort-job". I then click "Print Test Page", it gives the job ID "Samsung-13". Now, http://localhost:631/printers/Samsung shows:

 Samsung "Printer not connected; will retry in 30 seconds..."
  Description: Samsung ML-2550 Mono Duplex Laser
  Location: Next to Tandoor
  Make and Model: Samsung ML-2550 Foomatic/Postscript (recommended)
  Printer State: processing, accepting jobs, published.
  Device URI: usb://Samsung/ML-2550

with the test page job listed at the bottom:

 ID           Name        User   Size  Pages     State
 Samsung-13   Test Page   root   18k   Unknown   processing since
Wed Apr 25 19:47:02 2007

I'm running cupsd in debug mode, but there's nothing in /var/log/cups/error_log which looks useful, just debug information for the web API. In access_log, the relevant lines seem to be:

 localhost - root [25/Apr/2007:19:47:02 +0100] "GET /printers/Samsung?op=print-test-page HTTP/1.1" 200 0 - -
 localhost - - [25/Apr/2007:19:47:02 +0100] "POST /printers/Samsung HTTP/1.1" 200 18600 Print-Job successful-ok
 localhost - root [25/Apr/2007:19:47:02 +0100] "GET /printers/Samsung?op=print-test-page HTTP/1.1" 200 3449 - -
 localhost - root [25/Apr/2007:19:47:05 +0100] "GET /printers/Samsung HTTP/1.1" 200 0 - -

/etc/cups/printers.conf:

 # Printer configuration file for CUPS v1.2.7
 # Written by cupsd on 2007-04-25 19:46
 <Printer Samsung>
 Info Samsung ML-2550 Mono Duplex Laser
 Location Next to Tandoor
 DeviceURI usb://Samsung/ML-2550
 State Idle
 StateTime 1177526575
 Accepting Yes
 Shared Yes
 JobSheets none none
 QuotaPeriod 0
 PageLimit 0
 KLimit 0
 OpPolicy default
 ErrorPolicy abort-job
 </Printer>

cat /etc/cups/cupsd.conf|grep -v ^#|grep [:alnum:]:

 Classification none
 DefaultCharset UTF-8
 DefaultLanguage en
 Printcap /var/run/cups/printcap
 PrintcapFormat BSD
 RemoteRoot remroot
 SystemGroup lpadmin
 ServerCertificate /etc/cups/ssl/server.crt
 ServerKey /etc/cups/ssl/server.key
 <Location />
 Encryption IfRequested
 Satisfy All
 Order allow,deny
 Allow localhost
 </Location>
 <Location /admin>
 Encryption Required
 Satisfy All
 Order allow,deny
 Allow localhost
 </Location>
 <Location /admin/conf>
 AuthType Basic
 Require user @SYSTEM
 Encryption IfRequested
 Satisfy All
 Order allow,deny
 Allow localhost
 </Location>
 HostnameLookups Off
 KeepAlive On
 KeepAliveTimeout 60
 MaxClients 100
 MaxRequestSize 0m
 Timeout 300
 Listen localhost:631
 Listen /var/run/cups/cups.sock
 AccessLog /var/log/cups/access_log
 ErrorLog /var/log/cups/error_log
 PageLog /var/log/cups/page_log
 MaxLogSize 1m
 LogLevel debug
 PreserveJobHistory On
 PreserveJobFiles Off
 AutoPurgeJobs No
 MaxJobs 0
 MaxJobsPerPrinter 0
 MaxJobsPerUser 0
 User lp
 Group lpadmin
 RIPCache 8m
 FilterLimit 0
 DataDir /usr/share/cups
 DocumentRoot /usr/share/cups/doc-root
 RequestRoot /var/spool/cups
 ServerBin /usr/lib/cups
 ServerRoot /etc/cups
 TempDir /var/spool/cups/tmp
 Browsing Off
 defaultauthtype Basic
 <policy default>
 <limit Send-Document Send-URI Hold-Job Release-Job Restart-Job Purge-Jobs Set-Job-Attributes Create-Job-Subscripti
on Renew-Subscription Cancel-Subscription Get-Notifications Reprocess-Job Cancel-Current-Job Suspend-Current-Job Re
sume-Job CUPS-Move-Job>
 require user @OWNER @SYSTEM
 order deny,allow
 </limit>
 <limit Pause-Printer Resume-Printer Set-Printer-Attributes Enable-Printer Disable-Printer Pause-Printer-After-Curr
ent-Job Hold-New-Jobs Release-Held-New-Jobs Deactivate-Printer Activate-Printer Restart-Printer Shutdown-Printer St
artup-Printer Promote-Job Schedule-Job-After CUPS-Add-Printer CUPS-Delete-Printer CUPS-Add-Class CUPS-Delete-Class
CUPS-Accept-Jobs CUPS-Reject-Jobs CUPS-Set-Default>
 authtype Basic
 require user @SYSTEM
 order deny,allow
 </limit>
 <limit Cancel-Job CUPS-Authenticate-Job>
 require user @OWNER @SYSTEM
 order deny,allow
 </limit>
 <limit All>
 order deny,allow
 </limit>
 </policy>