hey guys,
i had similar struggles, but now have:
PBg4 (tiger) and a macbook air (leopard) printing wirelessly (bonjour USB connection through a NEW airport extreme "n" model) on a Canon iP3500 printer.
1. downloaded latest drivers at "http://www.usa.canon.com/consumer/controller?act=ProductCatIndex1Act&fcategory id=103"
for leopard, I downloaded the latest driver from the canon website. I chose the CUPS version (what this means, i don't know - they just said it was better for "air mac" printing, which is the Japanese version of "airport," i think)
for tiger, i used the latest regular driver (non-CUPS!).
2. connected printer to airport extreme via USB, turned it on
3. i installed as indicated on my respective hard drives.
4. opened prefs > print & fax
5. erased previous print queues (highlighted my printer in the selection box on the left, clicked ➖. I had to do this because of multiple failed install attempts in the past.)
6. clicked ➕ to add a new printer
7. "printer setup utility" opened, showed Canon iP3500 available via a bonjour connection
8. highlighted, added it
9. the default driver was "Canon iP3500." THIS WAS THE PROBLEM IN LEOPARD (tiger worked fine). i switched via the drop down selection to "Canon IJ" driver, which was the only other option.
this solved the problem.
Hope this helps. I know lots of people have had difficulty with Leopard and airport printing.
Just to illustrate the magnitude of everyone's frustrations, check out this link:
http://www.ifelix.net/tech/1013.html
Hope this helps someone out there.
good luck!