Black screen when playing LR3 Slideshow, but can see pix when I drag slider

I made a MPEG4 using Lightroom 3.2 exporting to slideshow and when it opens in Quicktime, the slider plays (30 mins., 392 MB) but it is a black screen. However, if I drag the slider, you can see the photos. And if I drop the slider at a point in the video, it shows a photo but does not change to the next photo, but the slider continues to run.

Both Quicktime and Lightroom updates were run.