why on earth, when my pc is put into hibernation mode, does the bloody thing turn back on again within a couple of seconds?

I wanted it to record some TV last night that didnt start till 10 to 1 in the morning, and in hibernation (according to the help and support thingy built in) you can do this. But the thing wouldnt stay off, so i couldnt.

Does anyone know if there is some kind of setting im missing, as i had a look in power options in control panel and there doesnt seem to be an option for anything like that.

Cheers in advance