Lightroom 5 slideshow shows a black screen
When I preview or play a slideshow in Lightroom 5 I see a black screen. I've tried it using various settings, images, lengths, and with the show saved or unsaved, all with the same result. In a preview I can see the show advancing through the slides; all remain black.
Sometimes (unpredictably) the screen isn't black, but rather two colors or color washes separated diagonally.
There are no videos in the shows. (A black screen for a slideshow with a video as the first slide is a known issue mentioned in the Lightroom Journal.)
Exporting to pdf works properly. An exported video shows as a black screen.
(Mac Pro, OS X 10.7.5, Radeon X1900 XT video card)
