coordinate system - Changing prime meridian of map?

I am working with the Natural Earth world map as a SHP file, but when I try to change the prime meridian (PRIMEM) of the coordinate system

GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]

I get this:

Projections seem to give the same results. What is happening here?

Answer

you might try exporting the data or possibly run it through a fix geometry (I use et geotools).
It looks to me lie with the new meridian you are splitting some polygons and that is causing the fill to "leak" out.