Strange problem where having set up my printer (an Epson CX5400) and had it working for ages,certainly in excess of 12 months, it suddenly doesn't print anymore. Scanning also doesn't work, almost as if there is no longer any comms between my box and printer. But, mtink works fine, and the output of lpinfo is as follows:-

serial serial:/dev/ttyS0?baud=115200
serial serial:/dev/ttyS1?baud=115200
serial serial:/dev/ttyS2?baud=115200
serial serial:/dev/ttyS3?baud=115200
direct usb:/dev/Stylus%20CX5400
direct usb:/dev/usb/lp1
direct usb:/dev/usb/lp2
direct usb:/dev/usb/lp3
direct usb:/dev/usb/lp4
direct usb:/dev/usb/lp5
direct usb:/dev/usb/lp6
direct usb:/dev/usb/lp7
direct usb:/dev/usb/lp8
direct usb:/dev/usb/lp9
direct usb:/dev/usb/lp10
direct usb:/dev/usb/lp11
direct usb:/dev/usb/lp12
direct usb:/dev/usb/lp13
direct usb:/dev/usb/lp14
direct usb:/dev/usb/lp15
file cups-pdf:/
network smb

The only changes I have made is a kernel upgrade from 2.10 to 2.16.
So I rebooted into 2.10, and still no printing. The error logs don't mean a lot to me, but if anyone wants to see them I am happy to post them here.

Anyone come across this problem, and have a cure?

Just a quick update, the Epson utility ekpstm, which is basically a monitoring util for the printer also see it OK and is able to send control messages i.e. clean print head, print test etc. Even more curious.

Probably the filter that CUPS uses to format the print job is broken. If you set the LogLevel to 'debug' in cupsd.conf, you should get more useful errors in the CUPS error_log.