I just recently tested my Dell. I experience the exact behavior as Jonathan and Andrew: memtest86 throws a bunch of errors then locks up.
I'm going to have faith in Dell and let it be for now. Weighing in that decision is that I just don't have time to return and buy a new computer for my mom (she'll be using it on her clinic).
Can someone confirm to me the type of RAM that I need to get for this machine? I don't know where my invoice is and need to purchase some more.
-Roberto