I am using the AMD firepro w4100 video card as previous poster. I drive two 4k monitors and third monitor at 1080p.
I had this issue with Izotope NEutron and also worked with their tech support but had no success. What I determined was that on some of my larger cubase projects Neutron would’t load at all on the inserts or the gui would open but wouldn’t populate with any image. It appeared to me that the problem was more evident if I had already had an effect in that slot and then deleted it to replace with Neutron. I am speculating here but the problem seems more frequent if the deleted effect had a corresponding automation and had been moved around in the insert slots .
I found that if I created another audio track from scratch I could get neutron to load on that channel and in some cases it would allow me to drag that instantiation across to the actual track where I wanted Neutron to open which had previously failed. Perhaps this workaround will help you.
Recently I have begun to reduce my larger projects to stems. Starting fresh seems to cure the loading issues… it is again a workaround but I have had to go there.
I should point out that the problem is not limited to Neutron and I have used the same workaround for some Waves and plugin-alliance plugins. I have a lot of RAM and CPU headroom available when this occurs as I monitor this closely when any workflow issues occur in Cubase. I run 32 gigs of Ram and a 12 core rig on Windows 7 64 bit.