title: XCode error "The application bundle does not contain a valid identifier."
body: <p>Recently, after upgrading to Lion and Xcode 4.2.1 I am getting this error when trying to run my app on my iPhone 4S:</p>
  
  <p>"The application bundle does not contain a valid identifier."</p>
  
  <p>My identifier is indeed valid, and I have been able to run my app with this identifier earlier.</p>
  
  <p>The problem might appear when I change computers.
  I have two computers that I am using to code my app, and I am using Dropbox to keep track of my files.</p>
  
  <p>Restarting XCode, my mac and my iPhone does not work.
  Cleaning the target and rebuilding does not work.
  The only thing I have been able to do to fix it is to create a completely new project and moving my files. This made things work until I swapped computer. Now I am in the same trouble again.</p>
  
  <p>Any idea? Anyone?</p>