Dear all, I have used my ultimate 11" on usual mirrored display on battery power and in clamshell mode. A few hours ago, I was running many apps in mirrored mood and my air just began to lag so badly after an hour. Expose is slow as well as surfing and clicking. I wondered what happened. Then I plug back power supply and close the lid of Air, hence running in clamshell mode. It then returned to full speed. Please help explain to me if title is true. It is disturbing to learn that plugging into to ext monitor could lag.