I do not think my problem is related to memory. I have plenty of memory (128 GB) and this blank GUI issue happens also after starting up the computer, starting Cubase, create new project, add one single audio track, add a single waves plug-in and open its GUI. If the last stored screen position of that plug-in is on the “wrong” (i.e. not on the Windows primary) monitor, it freezes (as does Arturia, VSL MIR etc.). At that time, the memory consumption is virtually zero. And I should add that, as long as the GUI is not open on the “wrong” monitor, the plug-in works perfectly in terms of audio processing.
I tried to install the oldest drivers I could locate on the AMD site, which was not very old (June 2015), same thing. I think it is a combination of Windows 10 (remember that I did not have these issues under Win 8.1, same graphic adapters, Waves 9), multiple displays, and a bad implementation of OpenGL usage either in the display driver or in the plug-in/software. I have seen things like this (https://mollyrocket.com/casey/blog_0032.html) but do not know what that means - this is a topic plug-in and driver programmers should take care about. They do not seem to test their plug-ins on secondary displays in a Win 10 x64 environment, which became even more likely after I recognised that the same happens with the latest NVIDIA NSV 810 drivers.
I do not know what others use - Cubase itself, other plug-in vendors like NI. Maybe they have done a correct implementation of OpenGL usage or they are using a different API for their screen outputs, like DirectX or whatever…