MacBook Pro Insomnia - Black Screen

System Specs

Lion 10.7.4

MacBook Pro 13" mid 2009

When my MacBook Pro goes to Sleep, it now has great trouble coming back to life again. The computer appears to be switched off, move the track-pad, click it - nothing. But press the volume keys and you hear sound... its still on and running. Sometimes its off like this and plays music, I close the laptop and it music continue to play without stopping. I have to shut down the computer off via the power button.

Sometimes I have to turn it on and off multiple times using the power button until I am given enough time at the login screen as it appears to switch off automatically after a few seconds. To break this cycle I click on either Restart or the Shut Down buttons at the login screen, the computer goes off I wait, I then switch it on it loads up as it should.

I need this computer to work with so fixing the problem(s) is quite important to me. All help appreciated.