Object Disappears in Layout
 

I'm trying Global ilumination for the 1st time and have a plane 100m x 100m with a skydome - doing the Newtek tutorial. When I bring the camera close to the object I want to render the object seems to disappear in the Layout view - gradually erase as the camera moves closer like a clipping plane is passing through it.

The light that I have turned off and the camera both seem rather large in layout - why is that? Does that have something to do with my issue?

Yes, OpenGL is clipping the object due to rounding errors. You'll find that the object will still render OK, just doesn't display in Layout properly.

Try changing the grid resolution with the '[' and ']' keys to see if this makes a difference.