Standby won"t wake up

When I select standby by computer goes to sleep. When I try to wake it up
with the mouse or keyboard it will not work. The drives and monitor are
functioning though. I can even open the DVD/CD drives. I end having to hold
the power button and restart. I've disabled Hibernate thinking that be it.
I've enabled keyboard to wake it up in the device manager.
--
Brandy