title: NSTimer thread issue
body: <p>I have singleton that implements NSTimer object.</p>
  
  <p>I run my timer using code below </p>
  
  <pre><code>self.myTimer = [NSTimer scheduledTimerWithTimeInterval: 1.0
                                                          target: self
                                                          selector: @selector(onTick:)
                                                          userInfo: nil repeats:YES];
  </code></pre>
  
  <p>I have <code>NSUInteger</code> instance variable that increase at each time when <code>- onTick:</code> method is called (so, once a second).</p>
  
  <p>I have <code>UILabel</code> that represents date of my  <code>NSUInteger</code> instance variable and it works good. I have <code>UIScrollView</code> in my view as well. When I am scrolling it my <code>UILabel</code> does not update text. Even NSLog that shows info about timer tick in <code>- onTick:</code> method does not work. If I don't scroll timer begin works. </p>