Try switching to a different view type (Shaded with Edges, Hidden Lines Shown, etc.) and then back. That often solves the problem for me. Which version of SW are you using? It happened to me this morning, but that was the first time in months. It was much more prevalent several releases back.
Thanks Glenn, I did try that. (without success). I also tried rebooting, etc.
We found something significant a few moments ago.
In sheet metal parts using a sheet metal extruded cut is better than a feature extruded cut. I had used a feature extruded cut on a sheet metal part. It showed no error but on close examination I saw that a formed edge after the feature cut looked oddly translucent. I deleted the cut feature and reused the remaining sketch to create a sheet metal extruded cut and all is well now.
I have to avoid using feature cuts in sheet metal parts, especially when the cross bends and edges.
Hope this is helpful to some.
I also have a similar "artifact" show up in our drawings from time to time. We have gotten the drawing view to show up again by deleting the view then undoing it. Ridiculous I know but it solves it.