Stand-by indicator light stays on

Last night and today I noticed on my Macbook (white) on the front, the white ambient standby light that pulses on and off, now is always on (steady solid white light). Then when I close the lid it stays on for maybe a minute or 2 then shuts off completely, taking the computer right along with it too. so my computer just turns off when it goes in sleep mode. Does anybody know what could be causing this problem and how can i fix it?

Thanks..