Terrain Material Black!

Problem remains. I have visible Terrain now, but when i start doing a sculpt a section of the terrain goes black.

://fs1.directupload.net/images/150308/lui2jijp.png

It is very odd why this works in a blank Project but doesnt in the FP game example.

ok i figured sth out.
Started a new FP example map. Turned off light affects the world. -> turns black again
BUT in a blank Project, if i turn off light affects the world i am able to sculpt without the blackness.
MAybe it has sth to do with the preset lihgting conditions, like lightmass important volume. reflection capture…