Heard this twice now. First time I heard it a few weeks ago I was in Windows via Parallels and just thought that was it. It hadn't done it again until tonight. I was just watching a video, the screen scrambled and then 3 long beeps followed by a pause then 3 long beeps, etc. My MBP boots as normal and all is fine now. Getting conflicting info on what 3 beeps means. Memory? 6 months ago I upgraded from 4gb to 8 myself. I'll check the modules if that's what this sound code means.