Windows 7 - Laptop locks up when monitor turns off

In the past i've been able to go into sleep or hibernation on my laptop no problem but recently my laptop stop letting me do that. Whenever i close the lid and the monitors turn off to go into sleep, because i set it to do so, the screen would turn off but the system would still be running with the monitor off. It's like the laptop is just running with the monitor off. No matter what i do i can't get the monitor to appear again or can't get the laptop to go into sleep or hibernation mode. I would have to do a hard restart to get the laptop back up. It uses to work before but i dont know what caused it to do this now. Here are some links that also explains the problem:

http://forums.toshiba.com/t5/Windows...ff/td-p/169770

http://social.technet.microsoft.com/...-14baf2aee3b2/

Please help. My laptop is a HP dv6 Select Edition if that matters. I bought this back in like August, so it's still fairly new.