I've been using an external charger since christmas as the phone wont allow for charging.
I have two batteries and they're both fully charged.

1 - power on Nokia N900.
2 - LED Lights WHITE.
3 - SOMETIMES the phone's backlight alone comes on and one vibration is felt. OR The Nokia logo will come up with the vibration then the LED light WHITE will come off. Both bootings repeat for a few times and then it shuts off.

When connecting to the PC, the NOKIA logo and the USB sign at the top right appears but the phone then reboots again so the USB device is not recognized as the device was switched off by itself.

The flasher does not, at all, recognize the device.