Could be Scheduled Tasks starting to stop them from waking up the computer, type "Task scheduler" in the start menuu, once there, click "task scheduler library" over in the left hand pane. Then look through scheduled tasks, right click on them one by one and select properties Then, Conditions tab and make sure "Wake the computer to run this task" is not checked.
Sorry for the bad spelling, my keyboard needs a slight cleaning
Cheers,
Mitchell