White lines through screen

I have a problem. A few weeks ago the camera on my Macbook stopped working. It wasn't showing up in the system profiler or anything. I am covered with Apple Care, so I made an appointment to take my computer to them to get it fixed. They said they needed to replace the camera, so they kept it a few days. Over the course of their repairs, the accidentally broke the screen causing a longer delay. I got the computer back on Thursday and have noticed a problem with the display ever since. Every so often, the screen just has these white lines run down through it. Sometimes its at the bottom of the screen, sometimes its in the middle, etc. It only is there for a few seconds and then it goes away. Obviously there is something wrong with the computer, but I cannot get it to do it long enough to be able to take it in and show them the problem. Any suggestions as to what to do because this is very annoying that I'm having more problems after what happened while my computer was at the Apple store.