guys, from past a week my phone has been turning off whenever i close the keypad or when i hit the n900 from outside. ( im not hitting it with a rod or a big stone, just a tap).

someone told that due to water content in n900, this problem. actually ive been cleansing the usb port of both charger and n900 with water because it keeps getting covered with dust. so there will not enough voltage flow to charge the n900. i have been doing that for a couple of months but there wasnt any problem. now, all of a sudden i often see my n900 switched off!

It is most likely the contacts on the battery. Take the battery out and use something small and thin like a pin or needle to bend the contacts back together.

oh i had similar problem the solution is the battery is loose so it keeps moving about and looses the battery connection touch on pins best thing to do is at the bottom of our N900 where the battery fits inside there are two metal strips slightly bent located preety much at the end of left and right side just bend them a bit more outwards first put your battery in then with small flat head screw driver lightly bend them towards the battery so it helps hold battery in place and if battery doesnt move about your phone wont sitch off!
hope this helps you enjoy back your n900 as this problem gets soo annoying!

I had this so superglued a thin layer of plastic to the bottom of the battery