I really don't know why it happens. 'Art brush original' in second picture is art brush material for art brush in both pictures.
In the first picture, the circle has no fill, and it's showing white fill as if it has.
And the second picture, as you see, something's gone horribly wrong.
I'm not really sure but this hadn't happened till the latest update(I might be wrong).
download link for second example: [download]