I had exactly the same issue with my Dell E6410. One day both shift keys just suddenly decided not to work. Again like with others, on USB attached keyboard everything was fine. I've downloaded the keyboard test tool and both shift buttons weren't present. I even booted up Linux CD to prove beyond any doubts that it's not somehow Windows related. After all of that I was ready to buy a new keyboard, but decided to wait until Monday, to do the final test at work with another E6410 keyboard. You can imagine how surprised I was when the following morning everything was back to normal - both shift keys work like a charm again. What's the cause? I still believe that it is somehow hardware related, so maybe sooner or later I will have to buy another keyboard, but if you're in similar situation, my advice is to wait a day, before you place an order.