I too have this issue. The slideshow has not worked in any version of Lightroom 5 from the beta up through 5.2. I even tried the new calatlog thingy described above to no avail. Mac Pro - dual 3GB Quad core Xeon processors, 16GB RAM, OSX 10.7.5 and a Radeon 1900XT video card. What annoys me the most is no acknowledgement from Adobe on the problem and no fix at all. Lightroom 4 slideshow works fine, Lightroom 5 does not. What gives here, Adobe?
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