I don't think there's anything wrong with taking a stroll from your desk. It can be seen as unproductive, but sometimes just talking to colleagues gives you an insight into what they're working on and if they are currently finding it difficult to solve a problem. Alternatively, you might find out something interesting from them.
You might be able to fix that problem quicker, so helping them to solve it quicker will no doubt reduce the colleague's brain-drain. That is, their motivation may reduce as it takes them longer to find a solution to something which they find uninteresting.