HOLY COW!! I’d been struggling with this problem for the last three days. I had audio three days ago and then it stopped mysteriously during the ram preview. I, too, had been hitting either the ‘play’ button instead of the ram preview button or using the space bar to start and stop the action. Thanks to Dave LaRonde for his admonition to keep the fingers off the space bar and to Lee Foxworthy for discovering the fundamental mistake.