title: Symfony2 returns class does not exist on entity load
body: <p>I'm trying to load a object from my File entity, but symfony keeps returning 
  "Class Frontend\FolderBundle\Entity\Role does not exist", but i can use it from the subfolder entity without any problems or warnings</p>
  
  <p>I have the following entity's:</p>
  
  <pre><code>Frontend\FolderBundle\Entity\File:
  type: entity
  table: file
  fields:
  id:
    type: integer
    id: true
    generator:
      strategy: AUTO
  filename:
    type: text
  user:
    type: integer
  manyToOne:
  folder:
      targetEntity: Frontend\FolderBundle\Entity\Subfolder
      inversedBy: files
      joinColumn:
        name: subfolder_id
        referencedColumnName: id
  lifecycleCallbacks: {  }
  
  
  Frontend\FolderBundle\Entity\Subfolder:
  type: entity
  table: subfolder
  fields:
  id:
    type: integer
    id: true
    generator:
      strategy: AUTO
  name:
    type: string
    length: 255
  manyToOne:
      folder:
          targetEntity: Folder
          inversedBy: subfolder
          joinColumn:
              name: folder_id
              referencedColumnName: id
  oneToMany:
      files:
          targetEntity: File
          mappedBy: folder
  manyToMany:
  roles:
    targetEntity: Frontend\UserBundle\Entity\Role
    inversedBy: subfolders
    joinTable:
      name: folder_rights
      joinColumns:
        subfolder_id:
          referencedColumnName: id
      inverseJoinColumns:
        role_id:
          referencedColumnName: id
  lifecycleCallbacks: {  }
  </code></pre>
  
  <p>Getting al the role's a folder has from a subfolder is working fine. </p>
  
  <p>I have cleared the app/cache and the doctrine cache, but that doesn't do the trick..</p>
  
  <p>If you need more information/code fragment's please ask and i will provide them.</p>
  
  <p>Thanks in advance,</p>