I have a 2010 13" Ultimate. I connect it via HDMI to my 21" Acer monitor and it works fine. Today I noticed that the AC power was disconnected, and it wouldnt connect to my monitor. It was wierd, because if I opened the lid, it would connect and power the external in dual monitor mode, but it would not drive the external monitor as a single screen (I do have resolution set to 1080p. Once I plugged in the Magsafe, it started up the monitor no problem. Is this a known thing? I didnt think driving a slightly bigger screen would cause an issue like that, I figured it would drain the battery faster. Its usually not a problem to leave the MBA plugged in when docked to the monitor, but I happened to need the plug for something else this time. Is this how it should be or what?