MBP built in display won't wake from sleep.

Hi

I have a Mac Book Pro and I'm having issues with the screen not waking (i.e. is black) once the machine wakes from sleep.

I typically close the lid to put it to sleep and several times now (twice today) have found that when I lift the lid and hear the familair noise of the OS waking up and the HDD spinning I am also faced with a black screen. I have also noticed this problem when I have left the machine long enough for it to go to sleep whilst the lid is up.

The machine is definately awake as I can hear contacts coming online on Skype and it's not something daft like the brigtness being down.

My current work around is to hold the power key down and hard boot it which is obviously not ideal with regard to losing work!

I don't have any odd widgets which I have read could create the problem and I have a healthy battery (believe it or not).

Any advice would be gratefully received!!

Cheers.