Well I would either return the router to place of purchase if thats possible.
If not, RMA the unit and let them know that other routers seem to work and tested. If you do the RMA, I would by a different router, say from Best Buy or Frys, something that has a 30 day or longer full refund return policy and see if it will work better while you wait for the RMA to return. IF you do the RMA I would detail your settings do they know what to fix or look for. Not sure what else to offer here. Seem there is an issue with FW. DLink needs to know about this.