Stage light effect

Can anyone please suggest what causes what I can only describe as stage lighting.
I seem to have an intermittent fault on start up with my Macbook pro 15 4,1 O/S10.6.8.
The screen looks as if it has stage lighting along the bottom, with vertical beams, also at odd times I get an almost black screen.
I have found that putting it to sleep by shutting the lid, or using the apple menu, and then, opening the lid or touching a key to wake it up, brings it all back to normal !!!!

I have tried to upload a photo of this problem.

Thanks in anticipation

Hard to see - looks like our resize plugin still isn't working correctly - but my first guess is a graphics chipset issue. I'd be making an appt with someone at the Apple Store on this one.

It's an led issue. My 08 had that problem. Contact apple. Also, closing and reopening the lid may clear it