Quoting Nigel Kendrick support-lists@petdoctors.co.uk:
When setting up a raw queue on the CentOS box, it might be necessary to
edit couple of files in /etc/cups.
mime.convs - uncomment this line:
#application/octet-stream application/vnd.cups-raw 0
mime.types - uncomment this line:
#application/octet-stream
I was going to suggest this as it seems to always fix printing problems with me. Just a few additional notes:
After editing file: service cups restart
If you do a yum update and there's any update done to cups, a default
instance of the above file is put back in place and you have to re-edit the file.
I think I once managed to make the change permanent. But can't remember anymore what exactly I did. It was long long time ago. Something like checking I want the queue to be raw somewhere in system-config-printer. I think. Can't find it anymore.