Did you try to to deactivate the GPU acceleration?
Did you try to reset the preferences?
What did you try? And please give us some more details on the hardware and OS you use.
It locks the whole PC and I need to reboot to get out of it. No error is displayed.
If the whole PC is frozen and has to be re-booted, then this is almost always either a bad/corrupt/out-of-date video driver, or a hardware malfunction.
Make sure your video driver is up-to-date and not corrupted by (re-)installing the latest version.
Check your hardware for malfunctions.
Windows 10 64bit
GPU: AMD Radeon HD 6570
Drivers - up to date - version - version 15.7.1 (I even ran the AMD utility to check)
I had problems with the LR performance acceleration when it was introduced but that was resolved a long time ago.
I have just turned this off and HDR functions are now working.
So, I guess the bug has come back.
A history summary:
LR CC installed, GPU acceleration bug present so feature disabled
Many discussions with the Adobe developer and returning log files to him
New LR releases which fixed the bug
New AMD drivers also released
HDR working for many months.
Then a few CC updates
Now the HDR feature does not work - if the GPU acceleration is enabled.
So ... in my book, thats LR and not the video drivers
I tried the drivers but still no luck.
I had an update of Lightroom this week and now it locks up when switching from develop to library mode.
I cant access the preferences to disable GPU acceleration - it locks when the dialog is loaded.
I have reverted the video drivers without any progress.
So this weeks LR update has made things worse.
Is there a way I can disable the GPU setting without launching LR?
Yes, you can disable the GPU without launching LR.
In this document, please scroll down to the section entitled "Manually disable the graphics processor" and follow the instructions there.
Just an observation-
I have created a virtual copy of one image and used this plus the original
This will not work in Lightroom!
No matter how you might edit the virtual copy, Lightroom only sees ONE master image file from which to create the HDR. So HDR from one image is not possible. (it is possible in Photoshop because you would be 'exporting' two different pixel versions of the master file)
Lightroom requires two individual image files with different exposure metadata to allow "merge to HDR"