I think there needs to be a warning label attached to writers, especially those who get interrupted frequently. I find that it's not unlike taking the first bite of your meal at a fancy restaurant, savouring the flavour, identifying the spices to have, "How's your meal?" barked at you by the host. You choke on the piece of food, swallow it down in order to answer them in time to see them walk away. Lost is the savouring, the flavour and the spices. All you're left with is the taste of irritation on the back of your tongue.
This is no different than disturbing a writer mid flow of creativity. Except with a writer your more like to get a rather snappish response to the "What 'cha doing?" question. In fact, you might just get your head bit off.
So fair warning to those who live with, work with, love and are related to writers. If you don't want a serious melt down on your hands, think about what the writer in your life is doing before asking any questions, particularly those that could be considered obvious. It might just save your life. ;p