I was just thinking...it's possible that you might be replacing it with another DS from a faulty batch? The store would probably have DS's from the same batch so you may continue to get dead pixels.
I'd suggest just taking it back for a new one again..maybe it will be 3rd time lucky. If it continues though..i'd ask them to ORDER a new one in. It will be a pain in the butt waiting on it but you should end up with a completely perfect DS.
27/07/2007
Trauma Center: Under the Knife
Adelaide, Australia