When we got home from the winter light show at the Idaho Botanical Gardens tonight the trackpad on the MacBook Air was unresponsive. I think it's happened before, though that may be a memory effect, my memory that is. At any rate I managed to use the keyboard to shut down and restart the laptop. Once I did I found out this symptom can indicate a bad ground. The Apple knowledge base article suggests if you can fix it otherwise you should wrest your palm on the wrist-rest. Um thanks but I'm not sure I really want to be the the ground.