Atmel SAM3U does not retreive data via USB-CDC

Hello!

I have a board with atmel sam3u mcu. Unfortunately, I didn't find USB-CDC example for this mcu, so I ported example for MCB2300 using some USB code from USB-HID and USB-MSC examples which are available. USB and CDC initialization works fine, data sending works without problems as well. But I have problems receving data via virtual COM-port. When I try to send data from terminal application on my PC it just reports communication error (tried other terminal applications - some of them just freeze, some also give errors). I suppose the problem is here (usbuser.c):

/*
 *  USB Endpoint 2 Event Callback
 *   Called automatically on USB Endpoint 2 Event
 *    Parameter:       event
 */

void USB_EndPoint2 (U32 event) {

  switch (event) {
    case USB_EVT_OUT:
      CDC_BulkOut ();                /* data received from Host */
      break;
    case USB_EVT_IN:
      CDC_BulkIn ();                 /* data expected from Host */
      break;
  }
}

I set a breakpoint and it seems that USB_EVT_OUT event is never raised, so CDC_OutBufAvailChar reports 0 bytes in buffer and so on.

What can I check? Maybe some misconfiguration?

Thanks a lot!