4.5k R3D editing works fine (limited to 4k project size).
I have noticed that each time I updated my Nvidia drivers, I got a different glitch. Once, I had a small # of footage go black randomly during playback like discussed above(all shot on older builds without new color science). I updated the video drivers and it went away, but it introduced a new glitch where playback would randomly flash a full 4k size in my 1k preview (which would sometimes show up in my 1080p renders). Again, this was on a small amount of footage with older builds.