UE4-9 crashing at launch

I tried to launch UE4.9.1, but it crushed in the process and this is part what the report said about it:

"Unknown exception - code 00000001 (first/second chance not available)

“Fatal error: [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.9\Engine\Source\Runtime\Engine\Private\Materials\MaterialShared.cpp] [Line: 1393]
Failed to compile default material WorldGridMaterial!”

Last time I used it worked just fine and next day this happens… What can I do?

This type of error was discussed earlier at another user’s question. I don’t know if this can be a decision of your problem, but just in case, try it. Unknown exception - code 00000001 - Community & Industry Discussion - Epic Developer Community Forums