Canon PIXMA MP640 on Snow Leopard - not showing up

I've just bought Canon's newest WiFi printer - the PIXMA MP640. Followed all instructions, downloaded newest drivers for Mac OS X 10.6X, installation went well until the Network Utility finished measurement tests and shut down.

Printer panel in Preferences shows the printer and scanner but the printer is shown as 'offline', despite the fact that it is online and connected wirelessly to the Airport Express (confirmed by the blue light on the printer).

Have tried everything I know to do - and no-one seems to have written much about this problem. Any solutions out there?

One weird thing I've noticed is that if you remove the printer from the list of devices and try and re-add it, the only MP640 device that is available is the 'MP640 Bonjour Scanner'. What's happening to the printer driver?

MacBook Pro 2.53GHz (a/b/g/n)
Airport Express (a/b/g/n)
Canon PIXMA MP640 (b/g)

I have also had problems with Snow Leopard and this printer. It will scan from my MacBook Pro on Snow Leopard but only goes through the motions of printing. I can add it as a printer, but only through Bonjour. Printer queue just tells me it's printing, but it's fibbing.

However I have a G5 Tower with is old plain old Leopard and that works perfectly, so I'm guessing it's a Snow Leopard/Driver problem. I have worked around the problem by sharing the printer from the G5, but it means that my G5 always has to be on, which is wasteful and not very satisfactory.

Hopefully this will get fixed.

Les