title: Plug-in com.android.ide.eclipse.adt was unable to load class android
body: <p>I am new to android development
  My eclipse was working properly. But now when I start a new project it give an error
  Problem opening wizard
  The selected wizard could not be opened</p>
  
  <p>The Detailed error message is</p>
  
  <pre><code>The selected wizard could not be started.
  Plug-in com.android.ide.eclipse.adt was unable to load class com.android.ide.eclipse.adt.internal.wizards.newproject.NewProjectWizard.
  An error occurred while automatically activating bundle com.android.ide.eclipse.adt (239).
  </code></pre>
  
  <p>I can't run existing Android project also.But I can start a new java project and run.
  Why this is happening</p>