Viewport Resolution Suddenly Dropped

I was altering a shader when suddenly the HDR Outdoor Environment disappeared and the viewport resolution dropped on all cameras, perspective view etc. Not fixed by loading a previously saved version.
I have restored the HDR, but cannot get the viewport resolution back up.
Same in Aux viewport.
Rendering works ok.
I would be grateful for some help with this.
Thanks
NOW RESOLVED BY CLOSING D3D AND RESTARTING
Post edited by Patroklos on
Comments
D3D ? Are you talking about a different program or are you meaning Daz Studio?