Question

2009-07-06 06:49:13.666 Spark[9825:10b] -[<NSUserDefaultsController 0x137af0> valueForUndefinedKey:]: this class is not key value coding-compliant for the key hotKeyDisplayEntry.

2009-07-06 06:49:13.667 Spark[9825:10b] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<NSUserDefaultsController 0x137af0> valueForUndefinedKey:]: this class is not key value coding-compliant for the key hotKeyDisplayEntry.'

EDIT:
What I think caused the problem.

OSStatus MyHotKeyHandler(EventHandlerCallRef nextHandler,EventRef theEvent,void *userData)
{
    EventHotKeyID hkCom;
    GetEventParameter(theEvent,kEventParamDirectObject,typeEventHotKeyID,NULL,sizeof(hkCom),NULL,&hkCom);
    HotKeyController *controller = (HotKeyController *)userData;
    int l = hkCom.id;
    switch (l) {
        case 1: [controller->window makeKeyAndOrderFront:NSApp];  
            break;
        case 2: [controller->searchWindow makeKeyAndOrderFront:nil];
            break;
        case 3: [controller->entryWindow makeKeyAndOrderFront:nil];
            break;  
    }
    return noErr;
}

- (void)awakeFromNib
{
    //Register the Hotkeys
    EventHotKeyRef gMyHotKeyRef;
    EventHotKeyID gMyHotKeyID;
    EventTypeSpec eventType;
    eventType.eventClass=kEventClassKeyboard;
    eventType.eventKind=kEventHotKeyPressed;
    
    
    InstallApplicationEventHandler(&MyHotKeyHandler,1,&eventType,(void *)self,NULL);
    
    gMyHotKeyID.signature='htk1';
    gMyHotKeyID.id=1;
    if([[NSUserDefaults standardUserDefaults] integerForKey:@"hotkeyCodeMain"]!=-999) {
        RegisterEventHotKey([[NSUserDefaults standardUserDefaults] integerForKey:@"hotkeyCodeMain"], [[NSUserDefaults standardUserDefaults] integerForKey:@"hotkeyModifiersMain"], gMyHotKeyID, GetApplicationEventTarget(), 0, &gMyHotKeyRef);
    }
    
    gMyHotKeyID.signature='htk2';
    gMyHotKeyID.id=2;
    if([[NSUserDefaults standardUserDefaults] integerForKey:@"hotkeyCodeSearch"]!=-999) {
        RegisterEventHotKey([[NSUserDefaults standardUserDefaults] integerForKey:@"hotkeyCodeSearch"], [[NSUserDefaults standardUserDefaults] integerForKey:@"hotkeyModifiersSearch"], gMyHotKeyID, GetApplicationEventTarget(), 0, &gMyHotKeyRef);
    }
    
    gMyHotKeyID.signature='htk3';
    gMyHotKeyID.id=3;
    if([[NSUserDefaults standardUserDefaults] integerForKey:@"hotkeyCodeEntry"]!=-999) {
        RegisterEventHotKey([[NSUserDefaults standardUserDefaults] integerForKey:@"hotkeyCodeEntry"], [[NSUserDefaults standardUserDefaults] integerForKey:@"hotkeyModifiersEntry"], gMyHotKeyID, GetApplicationEventTarget(), 0, &gMyHotKeyRef);
    }
    
}

In the NIB I also connected a text field to a NSDefaultsController.

Answer 1

In general, this means that you are attempting to access a key called hotKeyDisplayEntry for some object, but that object has no such key. You have likely made a typo or minor logical error.