Macbook Pro Screen Issue

Hi - on two occasions in the last few days my Macbook has locked up and the screen suddenly had boxed horizontal colored strips, and the laptop made an intermittent beeping noise. I've attached a photo of what it looks like. When I shut the computer down and restarted it and it seems fine now. Does anyone have any ideas on what the problem could be? Thanks for your help...

Your problem is more likely to be intermittent memory or the logic board. Some of your memory is shared by the GPU. If you have sufficient RAM to enable the MacBook to run on one of the memory modules, test with just one installed, then the other. If it only fails with one particular memory module installed, that will be suspect. If the fault occurs with when either memory module is installed, it's likely to require an expensive logic board.