I'm trying to make my Canon Pixma MX350 network printer work with Lubuntu 13.04 with Gnome Shell 3.8 (already went through the other questions for this model).

Cups (or the Gnome printer manager) can't find it on the network just by scanning. I managed to add the printer to Cups though by specifying the MAC address manually. Still it doesn't respond to print jobs. Cups says (or the printer is saying to Cups?):

"cannot specify model number."

I've used the 32 bit driver on my 64 bit Lubuntu in the past, a much older driver though downloaded from Canon.
Sometimes it worked, sometimes it didn't. So due to recent total refusal of the printer to respond, I removed it from the system and now I'm trying to reinstall it with a newer driver, from this ppa. Still 32 bit though as that repo doesn't have the 64bit flavour either.

This printer does accept print jobs though from Ubuntu and Windows on another machine on the same network. Ubuntu has it installed with the older driver. Here is a longer error log from Cups: http://pastie.org/8101197.
Now I went back to the old driver because it works on Ubuntu on the other pc. I also switched the printer connection from Wlan to wired LAN to exclude wireless flakiness. The Cups error message then turns into:

"cannot load library"