Most of the work we do (in software) requires uninterrupted concentration. Here are some thoughts on why being in the office is often more distracting than not from Jason Fried. I think he makes some interesting observations... have a watch. While your at it, take a trip over to Boycott A Meeting Day.
One of the things Jason points out that may help is using more passive means of communication such as email and IM to help to alleviate the constant interruption that can happen in our daily work life. I tend to agree with him with the exception of this observation... and that is this doesn't work if you are in an organization whose culture believes that email and IM trumps whatever else you are doing. But it definitely depends on the culture of your organization. In an organization that has a culture where IM and email trumps all else, you're going to have a hard time getting anything done in my opinion let alone blocking out time to concentrate on a problem.