I have the MP560 with the Canon CUPS driver software 10.30.3.0, dated 2/25/2010. I've installed it both wired and wirelessly, so I can print via USB in the den, as well as wirelessly from anywhere in the house.
When I use Copy from the front panel, print jobs sent from the computer just go into the appropriate print queue (wired or wireless).
Once the Copier function from the printer front panel is finished printing, the print jobs sent from the computer just resume automatically.
The MP560 shows the message 'printing from PC' when a print job from the computer is being processed, and the front panel controls are disabled.
What shows when you click on the printer icon that shows up on the Dock during printing?