title: NoClassDefFoundError - Rejecting re-init on previously-failed class
body: <p>Please somebody explain me what this error means and how to avoid it.</p>
  
  <p>After a while my app Force Closes because of this error:</p>
  
  <pre><code>09-28 12:53:45.746 I/dalvikvm(29489): Rejecting re-init on previously-failed class Lcom/bartat/android/ui/task/AsyncTaskExt; v=0x0
  09-28 12:53:45.748 D/AndroidRuntime(29489): Shutting down VM
  09-28 12:53:45.755 I/am_crash( 1146): [29489,com.bartat.android.secret,572996,java.lang.NoClassDefFoundError,com.bartat.android.ui.task.AsyncTaskExt,CommandsActivity.java,726]
  09-28 12:53:45.755 I/am_finish_activity( 1146): [1079225264,123,com.bartat.android.secret/.CommandsActivity,crashed]
  09-28 12:53:45.750 W/dalvikvm(29489): threadid=1: thread exiting with uncaught exception (group=0x40015560)
  09-28 12:53:45.752 E/AndroidRuntime(29489): FATAL EXCEPTION: main
  09-28 12:53:45.752 E/AndroidRuntime(29489): java.lang.NoClassDefFoundError: com.bartat.android.ui.task.AsyncTaskExt
  </code></pre>
  
  <p>This problem couldn't be solved by reinstalling the app. </p>
  
  <p>If I rename the <code>AsyncTaskExt</code> to <code>AsyncTaskExt2</code> for example then it works again for long. But after a few weeks/months it started to get this error again.</p>
  
  <p>What does it mean? Why it is thrown and how to avoid it without renaming the class?</p>
  
  <p>Please help me,
  Tamás</p>