crash in textFieldShouldReturn

Precisely I am having this error

[<MyViewController> _clearBecomeFirstResponderWhenCapable] -- NSInvalidArgumentException Unrecognized selector sent to instance

What is _clearBecomeFirstResponder?

I am creating a couple of views manually in my viewcontroller - On the similar lines of UICatalog. I create a text field and set my view controller as delegate.

Here's the code

CGRect screenRect = [[UIScreen mainScreen] applicationFrame];

// setup our parent content view and embed it to your view controller
UIView *contentView = [[UIView alloc] initWithFrame:screenRect];
contentView.backgroundColor = [UIColor colorWithRed:.56 green:.071 blue:.067 alpha:1];//[UIColor blackColor];
//loginTableView.backgroundColor = [UIColor colorWithRed:.56 green:.071 blue:.067 alpha:1];

contentView.autoresizesSubviews = YES;
contentView.autoresizingMask = UIViewAutoresizingFlexibleWidth;

self.view = contentView;
[contentView release];

// create the UITextField

refTextField = [[UITextField alloc] initWithFrame:textFrame];

// set the various properties here
.....
// now add the text field to the view

[self.view addSubview:refTextField];
refTextField.delegate = self;


Is there something I am missing? I've set the proper delegate and implemented this protocol method

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
if ( textField == refTextField ) {
NSLog(@"came to delegate method for UITextFieldDelegate");
[self resignFirstResponder];
}
return YES;
}

But when I click the return button, the above error comes.

Thanks in advance.