I have a couple thoughts about your question and since I am near to President privileges I will go ahead for the activity points and express them.
Large changes in volume, up or down, without a price change is not indicative of anything news wise. When a lot of people or someone with alot of shares decides to act on information, they stampede, they do not trade in ranges like happened that day.
I have seen this behavior when a market maker is trying to stir up investor interest when there is a flood of news or shareholders are anticipating a PR of some good news. They will buy/sell to themselves or a sister house trying to infer that someone knows something good or bad that you do not, a so far legal way to influence the market in that one stock up or down.
Of course it could be just that really odd day when there happened to a large amount of buyers and sellers happy with that price. Who knows? Ron