Today all of my renders of cylinders have been rendering as polygons. I have increased the image quality to the maximum value (Document Settings>Image Quality>Shaded and draft Quality and wireframe sliders). This does not however seem to make a difference. Prior to today, all was fine, and renders were great.

As a note, I have restarted a few times, and tried different parts, all with the same outcome.

Any ideas to take my circles for polygons back to circles?