Hi bobomyrat, hi folks.
Make sure that you have the latest driver for your graphic card.
Try choosing the anti-aliasing setting with the highest number.
On your image I see that you have highlighted one with 0X in the rightmost column. Try a 2X or even a 4X if one is present.
Click OK to validate then, to be really sure, quit SketchUp and restart it.
Just ideas.
Jean