My two bits: If your Green Card is valid you should be able to get back into the country. Whenever I have returned to the U.S. they seem more interested in my Green Card than my Passport. It looks like they use the passport to verify visually that you are who you say you are and use the Green Card to ensure you are legally allowed to enter the country.
My last trip to Canada I renewed my passport while in Calgary and didn't have it with me when I crossed the boarder (driving though). They wanted to see my Green Card though.
Don't mistake this as a guarantee, but bring your Driver's License, Green Card and expired Passport and you might be o.k. Try to get your expired Passport back when you renew and see if the customs officials spot the problem.
|