Strange EXC_BAD_ACCESS error in ObjC

Question

I know this error is relating to memory management. However, I can't work out what is wrong with the management.

With the following code:

id month = [monthsArray objectAtIndex:indexPath.row];
    NSLog(@"%@", [month class]);
    NSDictionary *dict = [logbookDataController summaryForMonth:month inYear:yearToView];

summaryForMonth:inYear is messaged correctly and the program runs. If I remove the NSLog, I get an EXC_BAD_ACCESS. I'm really confused as to why this would cause the error I get. Does anyone have any ideas?

Thanks.