What im suspecting is the unit is probo a year or so old now... correct?
Also you probally have ran the player down to empty so it shuts down all the time.
The batterys in the 402 are lithium ion (maybe poly but dosnt matter) and they dont like to be ran down completly, thus now the thing is giving u reduced battery life.
Even when the batterys are treated with kid gloves there is a finite amount of charges it will take, using the cam and usb host will also knock the battery life.
If you go to www.newmp3technology.com
they supply the batterys, this will solve the problem. They are suppose to be ok to fit (mine still running fine atm) but looking at it the terminals are soldered to the mainboard, when you get the battery chop off the old one leaving about an inch or so on the mainboard (attach the battery to these flyleads) as its a right pig to solder on the board plus it would be to easy to short out the terminals and cause damage to the payer itself.