Texture bugs in Editor

Hi,

I'm currently making a city building game and i'm having weird texture bugs in the editor. When it first loads, the terrain is black and the water texture/trees are not showing up at all. The GUI texts alsodon't display (they have default text in the editor which is overwritten at runtime)

To fix it i have to build the game and then come back to the editor. The below pictures show the before and after shots of that process (The white cylinders are place-holder models for rocks)

Essentially my question is :Has anyone experienced this before/know how to fix it

Any help would be appreciated