UIButton title text is not updated even if I update it in Main thread

Question

I'm trying to change the title of an UIButton I've created programmatically, when the user clicks in it. So, this is my code to create the UIButton:

myButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, parentView.frame.size.width, parentView.frame.size.height)];
[myButton setBackgroundColor:[UIColor blackColor]];
[myButton setAlpha:0.7];
[myButton setTitle:@"Hello" forState:UIControlStateNormal];
[myButton addTarget:self action:@selector(userClicked:) forControlEvents:UIControlEventTouchUpInside];

[parentView addSubview:myButton];

And, in my userClicked: method, I do:

-(void) userClicked:(UIButton*)button
{
    NSLog(@"USER CLICKED!!!");
    if ([NSThread isMainThread])
    {
        NSLog(@"is main thread");
    }

    [button setTitle:@"Bye" forState:UIControlStateHighlighted];
    [button setTitle:@"Bye" forState:UIControlStateNormal];
    [button setTitle:@"Bye" forState:UIControlStateSelected];

    [self someLengthyComputation];
}

The weird thing is that I can see the log messages printed:

USER CLICKED!!! 
isMainThread

But, the title of the button does not change! What am I doing wrong?

EDIT: Setting the title for several states doesn't work either.

EDIT2: If I print the description of button in the debugger window of Xcode, it shows the right title!

Printing description of button->_titleView:
<UIButtonLabel: 0xa4c9310; frame = (95 216; 130 22); text = 'Bye'; clipsToBounds = YES; opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0xa44f080>>

Answer 1

This worked for me to update the title text (iOS 7.1, Xcode 5.1):

button.enabled = FALSE;
[button setTitle:@"Test" forState:UIControlStateNormal];
button.enabled = TRUE;