HP Laptop... sometimes it seems to get stuck in sleep mode.......?

I have an HP Laptop (Pavilion dv6) an here is aproblem I am having. I close the lid then later when I open the lid in order to use it again, the screen stays black. All the lights on teh keyboard are still lit up and the fan works, but I cannot seem to get the screen to light up. If I do a hard shutdown, or even remove the battery and plug, once I start it up again it just goes back into this mode. I now feel lucky - when that happens - to even be able to do anything with it! I was lucky tonight I got it to boot up instead of go into that weird mode. What is going on?