In message <004b01c37fae$69127440$0192fea9@Main>, Sam Elsdon <sam.elsdon@...> writes
They are a remnant of country borders which vanish when using inverse
boundaries. As David explained to me, the coastal outlines and the country
outlines are treated separately and the process of exclusive ORing causes
the country outlines to disappear. But clearly, a few pixels remain. The
coastal boudaries are unaffected.
Don't worry, it is not your graphics card.
Many thanks Sam - understood. Won't try updating drivers!