There is an old trick to help you remember something; concentrate on remembering peripheral things, recovering the context, where you were and what you were doing, when you heard or saw what you want to remember. I'm not surprised that it works in reverse, changing contexts interfering with recall, as well.
http://www.springerlink.com/content/m6lq80675m22232h/
There's probably some deep implications to this I'm not qualified to plumb. But next time I'm concentrating on something, and need to get up from the computer and walk around a bit, I'm going to try avoiding doorways.