We need more information, bro.
Did it ever hibernate and now it wont anymore? If so, did you do anything lately, either software or hardware?
What are the specs on your machine? What hardware are you running?
What happens when you try to hibernate? Does it freeze or just kick you back to windows?
What's sleep mode, do you mean standby? So neither hibernate nor standby work? Can you do a full shutdown? Will the computer stay off when you do a shutdown or does it turn itself back on?