Canon Pixma MG6250 - CD Printing (Tray G)

Background

I'm running an iMac with 10.6.8. Previous printer was an HP C5380. Printing directly onto CD from with Adobe Illustrator was easy. Design the layout, select print and choose 'CD' as paper size. Done. The HP needed replacing and HP no longer have any printers with CD printing capability.m

New Printer

I got the Canon Pixma MG6250 and normal printing works as it should. This printer has a small tray (called 'Tray G') that you place the CD onto and then insert the tray into a slot (inside the main paper loading slot) This slot is accessed via a drop down 'inner cover' that you need to manually open. You then place the tray into this slot and line up two white arrows. The printer should then draw this tray inside and print. (This was how the HP printer worked too)

Problem

When I select 'File - Print' in Adobe Illustrator, I then select 'Media' and the option 'Disc Tray G'. I select this then click 'Print'

The printer displays an error saying 'Inner Cover Open. Close the inner cover and select OK'

When I do that I get a second error message saying 'Rear Tray. There is no paper. Load Paper and select OK'

Has anybody got a solution to this problem? It's driving me crazy................