To the OP:
What you are seeing is the result of the graphics engine's attempt simulate bokeh. Rather than applying a simple motion blur or Gaussian blur, the software is attempting to
emulate the way a real camera would render bokeh, with the tendency towards circularity in the highlights of out-of-focus areas. Because this emulation is more difficult to render than a standard Gaussian blur, the viewfinder does not use the full emulated bokeh in its preview and all you see is the simpler Gaussian blur when you're initially composing the image.
Obviously, the simulation is not perfect and in some situations the rendering can be problematic. In your specific case, the processing engine is having difficulty with the crosshatching in the roof tiles (the area directly over the drive's seat in the car) and with the many, close together, vertical lines in the cartoon bull image above the car's trunk. A simple Gaussian blur would not have this same difficulty in handling closely spaced parallel lines and that's why it looks OK in the preview. When you actually take the picture though, the processing engine attempts to emulate bokeh by generating circular out-of-focus areas around highlights and this can cause undesirable artifacts in areas with crosshatching or closely spaced parallel lines.
The process works pretty well in most cases, but as you've seen it can fall apart a bit in some circumstances.
It's worth noting that not all real life camera lenses render bokeh in the same manner either. Even discounting mirror lenses (which have god-awful "doughnut" bokeh), the bokeh produced by different lenses will vary. In some situations, a lens which normally produces nice bokeh will have bad bokeh just because of lighting quirks. For example, note the first photograph posted in
this thread. The lens in question is one of the best Canon makes, but in that particular situation it gave a very artificial appearing result because of a combination of lighting and background patterns. If you're interested,
Ken Rockwell did a comparison of several different lenses all at the same focal length and aperture and you can see that the bokeh changes from lens to lens.