I am wondering if it’s a LightMass bug or the hook from eVga Precision X 16. I took two pics before I read that with 4.9.x+ it caused issues but nothing like the discription. Pic with 96% CPU spike is from LightMass being at like 75ish but I didn’t get a shot and the normal but still completely locked and dead UE4.10 Editor with the Defualt Scene, and 1 tree and couple instanced grass meshes from the Vegitation content pack shared on the forum…had to task kill it.
link text