Why is UE4 crashing when pressing the "save" button?

Hi you! I have a very annoing problem when using UE4. I was in the texture editor and when i pressed the “save” button, the window showed a loading bar freezed at 0%, and after 2 min it suddenly crashed. It happens EVERY time i click the “save button”… Here is the crash report:

LoginId:30386af24a7d2728714b128224c929e3
EpicAccountId:5e374054a6ef4fd8b6a0c83f8ae3d261

Fatal error: [File:D:/Build/++UE4/Sync/Engine/Source/Runtime/Engine/Private/ShaderCompiler/ShaderCompiler.cpp] [Line: 2139] Failed to compile default material /Engine/EngineMaterials/WorldGridMaterial.WorldGridMaterial!

UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_CoreUObject
UE4Editor_MaterialEditor
UE4Editor_MaterialEditor
UE4Editor_MaterialEditor
UE4Editor_UnrealEd
UE4Editor_Slate
UE4Editor_Slate
UE4Editor_Slate
UE4Editor_Slate
UE4Editor_Slate
UE4Editor_Slate
UE4Editor_Slate
UE4Editor_Slate
UE4Editor_Slate
UE4Editor_ApplicationCore
UE4Editor_ApplicationCore
UE4Editor_ApplicationCore
UE4Editor_ApplicationCore
user32
user32
UE4Editor_ApplicationCore
UE4Editor
UE4Editor
UE4Editor
UE4Editor
UE4Editor
kernel32
ntdll

Hope someone of you will answer me ;(