I loaded the new firmware today into my PIXMA MX920 - re-registered with GCP and all is fine. It appears that the incompatibilty between Google and Canon was eventually fixed by Canon. Thanks guys.
Does anyone know what's happening with this issue? There does not seem to be any workaround or info update. I have had my Canon MX920 for about 5 weeks. Worked fine initially but now cannot Register for Cloud Printing (Server Error).Otther network...