To those who think 3DS R&D costs are causing this... The actual R&D expenses listed in the report have only gone up about 15% (and it's a minuscule amount anyways). The overall administrative expenses are actually down, so 3DS development is not having any effect on the bottom line.
The truth is:
-DS sales are down 50%.
-Wii sales revenues are down 25%.
-Software sales are down 20%.
-Foreign exchange rates are through the roof.
Without the foreign exchange rates Nintendo would still be making a profit. Albeit a very small profit, but at least not a loss.
This will probably all turn around for Q1 2012 when 3DS is selling boatloads of everything.