Getting objectForKey: in an NSDictionary with JSON data returning nil even though the key is present

Question

I'm making an iPhone app in which I retrieve JSON data from http://maps.googleapis.com/maps/api/geocode/json?address=canada&sensor=true, and then I store it in an NSDictionary object. My code compiles fine, and the JSON data is valid. However, when I look for certain keys, it returns nil even though the key is present and I'm not making a typo. This is the only key that works (feed is an NSDictionary object):

NSString *status = [[NSString alloc] initWithFormat:[feed objectForKey:@"status"]];

but when I do something like this:

NSString *longName = [[NSString alloc] initWithFormat:[feed objectForKey:@"long_name"]];

I get this error:

WebKit discarded an uncaught exception in the webView:shouldInsertText:replacingDOMRange:givenAction: delegate: * -[NSPlaceholderString initWithFormat:locale:arguments:]: nil argument

I have two questions: how can I fix this? Also, since this Google Geocoder can return multiple places if multiple places with the same name exist (i.e. "Springfield"), how can I choose which key I want to refer to? (like which "long_name", which "lat", etc…)

Thanks in advance!