The most common reason is that the DS has been dropped and the surface mount inductor close to RH shoulder button has been 'knocked off' due to the 'shock' and to the very poor soldering when manufactured. When you take the unit apart be careful you don't lose the component!! The component can then be resoldered back in position. I have found this always to be the case when a DS won't power up and 'something' is rattling around inside.
Rob, June 2010
