Similar problem here on MacBook Pro Retina, running OS X Mavericks 10.9.5.
On my computer, since upgrading to Lightroom 5.x over a year ago, both the Impromptu Slideshow (CMD-Return) and selecting the Slideshow Module from the Main navigation tabs has produced a completely black screen with no slideshow.
And today, after installing the Lightroom 5.7upgrade, the first thing I checked was the Slideshow module, and while it will set up a slideshow layout according to whatever parameters I have set up,when I then try to Preview or Play the slideshow, all I get is a completely black Lightroom window (Preview) or a completely black monitor screen (Play Slideshow) -- the same as with all previous versions of Lightroom 5.x.
I've noticed in various Adobe and other forums, that for a number of Lightroom users--but apparently not all users--this has been a persistent problem that Adobe has failed to address for almost two years now....
Very frustrating and disappointing situation...
Bob – many thanks for your reply. Whilst not clearing the problem it’s good to know it’s necessarily me ..... Since I posted the query I loaded LR on a laptop I also use and have found it works OK on that platform adding further support to your comments.
I have this exact same problem on my MacBook Pro. It's extremely frustrating.
A long time ago, I worked at Adobe, and I still have connections there. And, using those connections, I've been able to contact and work directly with a member of the Adobe Lightroom customer support team to troubleshoot the problems I've been having, both with the Lightroom 5/x slideshow module and also with cataloging video files.
The troubleshooting process was rather complex and took a few hours over several days to complete. It included removing all Adobe Lightroom related files from my user library folder, completely uninstalling Lightroom, enabling root admin access to my Mac, reinstalling Lightroom while logged in as the root admin, creating a completely new Admin user on my Mac, and copying some photo and video files from an external hard drive (where I keep all my original and processed photo files) to the Pictures folder of my new admin user folder.
After doing all this, I opened Lightroom while logged in as the new admin user and imported the photos and video files from the Pictures folder into Lightroom. The net result was that everything worked just fine. Cataloging video files was no problem, and the slideshow module worked perfectly.
However, when I logged out of the new admin user account and logged back into my own user account, all of the problems I've been experiencing with cataloging video files and the slideshow module returned. I even tried creating a new catalog in my own user space and importing some photos and video files from the Pictures folder in my own user space into this new Lightroom catalog--but to no avail.
While logged in with my normal user ID, trying to catalog videos hangs the import, and the slideshow module still shows only a black screen during preview or full-screen slideshows.While logged in with my new test user ID, Lightroom works perfectly.
The conclusion from all this testing is simply that some file(s), most likely located in my user library folder, are conflicting and/or interfering with Lightroom's video cataloging and slideshow functionality. So, it's not a problem with the Lightroom application per se. Rather, it's a problem with some other application or system-related files---e.g., QuickTime, which is used by Lightroom to process video files--interfering with Lightroom's functionality.
The challenge is identifying which file or files among the thousands of files in my user library folder are the culprits, which is literally like looking for a needle in a haystack.
One way to solve this problem is for me to do a CLEAN installation of my operating system, and then reinstall all my applications one-by-one. This would be a tedious and extremely time-consuming process, since I have well over 100 applications installed on my Mac. Another possibility might be to log into the new admin user account I've created and try opening various applications in combination with Lightroom to see if any of them cause the conflict. (Each time you launch an application in a new user account on the Mac, that application generates its own support and preference files in the user library folder for that account. Presumably, by identifying a list of possible conflicting applications, launching them one-by-one and checking Lightroom' s functionality in combination with each application launch, sooner or later, I would find the culprit. Of course, this might also be a tedious and time-consuming process.
I've seen enough reports in this forum and elsewhere to know that whatever is causing this conflict isn't unique to my computer. These same symptoms have appeared on other Macs and on Windows, but apparently the percentage of Lightroom users experiencing the slideshow problem is relatively small. Also, it's now clear that this is not specifically an Adobe Lightroom software issue. Rather, it falls in the gray area of software interactions, which from one perspective is an Adobe problem and from another perspective is not.
In any case, if and when I discover what is causing this conflict on my MacBook Pro Retina, I will post that information on this and other appropriate forums.
Thank you for that detailed response. I hope you can find it. Good luck!