albook not waking up

my albook is set to wake up in the mornings for my alarm program to play music and wake me up. this only supplements my clock alarm, but i still rely on it. i've been having a lot of trouble lately with the computer not waking up! and i'm positive i'm not sleeping through it since even when i sleep in from it not waking, i find it asleep even though my settings require it to stay running for over half an hour. does anyone know why it's not waking? hardware or system related? i want to find out soon so i don't have any more irritating mornings when i oversleep. and yes, i do in fact leave it open when in sleep mode!