Immigrant McCain?

An article in today's NY Times writes about the constitutionality of McCain's presidential bid. The question arises out of the meaning of "natural-born Citizen" written into Article II of the Constitution. John McCain was born in the Panama Canal Zone in the '36. Can you consider a child born of American citizens on a foreign military installment a "natural-born Citizen"? Personally, I'd be inclined to say yes, but then again, I'm not a constitutional scholar.