My pc had this issue for a long time and i'm tired of this, I want to solve it.
If I click on Hibernate, it will work but then the computer will turn on itself (5 secs after), with the hdd led on, it shows 'Resuming Windows',then I get the blinking cursor on the top left of the screen and I have to reboot manually.
Then it will ask me to continue with resume or delete resume and proceed with normal boot>this one will work.
It is running Windows 7 x64, I had same issue in 32 bit version.
I have disabled the power management thing in network card props.