I am getting choppy video on my Macbook Pro.

I know there are about 75 answers to this already, but nothing has worked.

I have Maverick. I just upgraded to 8GB of ram. 2.3 GHz Intel Core i7. I ran disk utility. I have updated Flash. I have plenty of memory. I have restarted in Safe Mode and the thing went really wonky. There were horizontal lines running up and down the screen. Trash is empty. Any more ideas?

Help!