If the above doesn't work you can disable it manually by browsing to your preferences file, open it with notepad finding the line "use AutoBahn" and setting the value to "false". The line is towards the bottom of the file.
The preferences file should be here: C:\Users\[user name]\AppData\Roaming\Adobe\Lightroom\Preferences\Lightroom 6 Preferences.agprefs
thank you for both of your helpful answers! I tried the solution with the preferences file. But it did not deactivate GUP accleration, but I was able to deactivate GPU now without crash.
Just for understanding: what did the value of "useAutobahn" change?
But I would like to see AMD oder Adobe the rootcause with the driver.
So thank you very much for your fast und very helpful answers!
This deactivates the GPU acceleration: On my system whenever I change if from true to false, and vice versa, the check box for GPU acceleration also changes in the preferences screen.
I wonder if you have a corrupt preferences file?
perhaps my file was corrupt indeed? After I changed the value Autobahn, all my preferences seem to be lost. LR did not remember which my last settings in LR...