I've had a very similar result with a couple of A3 prints, printing from a new canonPro 9000 mkII. When I printed the first one I at a loss to explain it, signing on to my the internet I noticed that the computer (Dell Laptop) showed "Not Responding" for a couple of seconds. I have since noticed this on other programs such as Word etc. I am currently going through the (long) process of removing each of my programs in turn to try and isolate the problem. It was on the second print that I noticed Lightroom was "Not responding", but as this has happens intermitantly and with other programs it does seem to be something general causing the corruption of the file, but the cause as yet ????
John