Hello, I would check if there are any new drivers/firmwares for the printer.
Does it use a different resolution in canvas?
Are the colors very bad if you state that you are using paper, but put canvas? (wild guess, sort of last try solution)
I have had this problem on my 7600 when printing large prints from my Mac (running SL at that time) The cause seemed to be a very long connection from Mac to Printer - I used an ethernet extender to send the USB signal to the printer. Sometimes it would stay connected long enough to print and sometimes not
So I would look at the nature of the connection - making it as short as possible for a test to see if it makes a difference - try using a new/different cable. Does the computer indicate a connection error when it stalls? look at the print status window to check this
The nature of this kind of error with a very large file being printed and hence a long print time would also suggest looking at the machine you are printing from to see if it has any power saving or sleep settings that might try and kick in. This is most likely on a laptop but could also happen in a desk top with a sleep setting. If this is a possibility try disabling any energy saving of sleep settings and try again. If you can't easiliy do that try going back to the computer every 5 minutes and jiggle the mouse to keep it awake while printing.