A beginner’s mistake:

*.h
@interface * {
NSMutableDictionary *myDict;
}
@property (nonatomic, retain) NSMutableDictionary *myDict;

myDict = [[NSMutableDictionary dictionaryWithObjectsAndKeys: ..., ..., nil] retain];

If NSMutableDictionary is created with NSMutableDictionary dictionaryWithObjectsAndKeys, and it should be retained, it has to been sent a retain message explicitly.

No alloc, no init, no retain…