By hanging I mean there are print jobs in the queue, printer is enabled, and printer was just working fine a few minutes before. A restart of cups usually fixes the problem, but some times need to lprm all the print jobs for that printer, and restart cups before it will start printing again.

Anybody ever run into this problem before, or have a solution?

System is RHEL 5.7 with latest updates.

Doesn't seem to matter how printer is connected, network, lpr, smb, or serial. Client has mostly serial printers, so happens quite regularly on a serial printer, but have seen other systems where print jobs hung in the queue for days or months, for no reason.

Thanks in advance.

Are there any clues in the logs ??? (/var/log/cups/access_log ? /var/log/cups/error_log ?)

The only thing unusual is this message in access_log:

access_log:localhost - - [27/Sep/2011:05:55:01 -0700] "POST / HTTP/1.1" 200 75 C
UPS-Get-Default client-error-not-found

but it is all over the place. Unless there is a problem with this error occurring too many times, I don't see this causing the problem. There are no other messages than usual in either file when the problem occurs.

I have turned on DEBUG2 level. The only thing I have found sor far is lpstat -l -o shows the a Alert of job-printing for the first job hung in the queue. Others show Alert of none. Nothing unusual in details of printer shown with lpstat -l -t.