For the past two weeks, I had been going back and forth to the Apple Store for issues with my MacBook Pro. The first week, they disregarded my statement that it was the hard drive and replaced my MacBook Pro's logic board. Since the problem came up again, they finally agreed to replace the hard drive the next week I went. Now for the third time today (this has happened in the past week), the screen goes to vertical blue lines across, and the audio from whatever I was doing begins to stutter. The only thing left to replace is the RAM, which I bought 3rd party. I ran memtest86 (runs inside OS X) and everything came back fine. Should I look to that as the last possible cause of my issues?