When and how to use switchTo() method in webDriver (Selenium 2) to handle window/pop up -

I'm having trouble clicking or interacting on some page elements. They look like normal dom objects just click here The code for one is

    
 After clicking on a button as "upload file", another pop-up window was opened. My work is to upload a file in the popup window and go back to the original window.  
 I  
 www.test.com (& lt; - made a name for example)  
 I have to login  < P> Try to start a WebDowner  
 Click Upload a File Button  
 Then click on the redirect instead above the top of our site www.foo.com, I I'm using the same built-in driver and I try to chat with the button on the post upload page  
 button.click ()  
 It's never been these buttons Power, but they are in firebug and appeared normal.   
 
 
 You can try switching back to the window again after the redirect.  
 Save the window handle:  
  string myWindowHandle = driver.getWindowHandle ();   
 You want to redirect to the page and then switch to the window call:  
  driver.switchTo (). Window (myWindowHandle);   
 Is there a frame in your page? It may also be possible that you are not in the right frame after the redirect.