Terminating app due to uncaught exception

Question

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[NSKeyedUnarchiver initForReadingWithData:]: incomprehensible archive (0x4e, 0x49, 0x42, 0x41, 0x72, 0x63, 0x68, 0x69)' 2010-09-03 16:58:20.522 CHI[1843:20b] Stack: ( 807902715, 2481118779,

-(void)loadView {

    [super loadView];

    [self textbox];
}   


- (void) textbox {
    txtUsername.clearsOnBeginEditing = NO;
    txtPassword.clearsOnBeginEditing = NO;
    [txtUsername setDelegate:self];
    [txtPassword setDelegate:self];
    txtUsername.clearButtonMode = UITextFieldViewModeWhileEditing;
    txtPassword.clearButtonMode = UITextFieldViewModeWhileEditing;
}   

Please help me