title: pngcrush caught libping error, but only when building for device
body: <p>I have some png files in my iPhone app project. They work fine when I build for the simulator. But when I build for the device, suddenly every single png file generates the dreaded "while reading such-and-such.png pngcrush caught libpng error: ... Could not find file: ..."</p>
  
  <p>As I say, everything builds and runs great with the simulator. It's only when I change the scheme to build for the device that I get the errors.</p>
  
  <p>I tried cleaning and rebuilding.</p>
  
  <p>I tried manually deleting the Products directory.</p>
  
  <p>I tried restarting my system.</p>
  
  <p>I tried using the files in a different project (same results there).</p>
  
  <p>The only thing I have found that works is to open the files and resave them. However, this is a less than optimal solution because I have hundreds of PNG files all suffering from this issue. I would rather understand what the issue is so that I can fix it directly.</p>
  
  <p>Any ideas? </p>