Iray View quit working, but only on one scene.

kyoto kid

...not sure what happened or what I may have done but while  working on a scene using Iray view mode (which I needed on for positioning decals) it suddenly stopped working and all I had in teh viewport were the "clay" images of everything in the scene (it didn't drop back to shaded mode).

If I moved the camera in and out it would come back but only momentarily.  I closed the scene, closed Daz, restarted everything but it still occurred.  The scene will render normally but I don't want to deal with having to do a tonne of test renders to get the decal positioned correctly, it just not display properly in Iray mode.  I tested other scenes and they worked fine which leads me to wonder if I did something wrong while working on the one scene that somehow shut the rendering feature off.

This happened a few minutes after I turned the denoising on but that should not have caused it to stop working as I've had it on before while in Iray mode and on more complex scenes. 

As I have a Titan X with 12 GB of VRAM this should not be happening. certainly not after shutting everything down, waiting a bit, then starting the Daz programme up again and reloading the scene.

ETA:

...yeah something is messed up with the viewport parameters in this scene and I don't know how that happened.  It seems to be locked on one preset as when I try other dimensions such as "square" or "portrait" the viewport active boundaries do not resize (however the scene will render in the new setting ).  This also seems to only be occurring in Iray View, not any of the other viewport modes.