Is that the blue flashing light?
If so thats related to the Sleep mode on the phone.
Try going to menu, tools, settings, phone and then display. Turn sleep mode off.
Sleep mode is a battery saving option on the phone. If the phone is not used for a period of time (I think its about 2 minutes) it goes into sleep mode and appears to be switched off. The blue light flashes so that you know it is still on.