Do you have the MP560 connected to the Mac via USB or wireless?
If it is connected via wireless, then you will need to ensure you have the scanner installed in Print & Fax and to do this you will need to install the MP560 scanner driver. Here is a link to the MP560 Scanner Driver.
With the scanner driver installed you can open Print & Fax and click to Add. The MP560 should be listed as a Bonjour Scanner. Select this and the Print Using menu will automatically select the MP560 scanner driver.
Next, the installation of MP Navigator. Here is a link to v3.0.4, which supports your MP560. With this installed you will have the Canon Utiities folder in Applications. Open MP Navigator and click the Preferences button to ensure the MP560 is listed. If it is, click OK and then you are ready to scan.
And as for Image Capture, that error can occur when the scanner driver is not installed. As for the message about the rear tray, that is just a coincidence that is showing - it is not in response the scanner error, although if you were to do as it says, the MP560 could be waiting for you to clear this current error (the loading of paper) before it performs your scanning.