Ran into the same issue here, It randomly fixed itself for a brief moment when I re-opened the level.
Went to continue working and tried adding a bit more foliage, it proceeded to crash and now it has returned.
It blows, as this project has been months in the works and I fear I would restart and just run into the same bloody issue.
I tried all the solutions above, re-installing, deleting Saved, Intermediate, DDC, duplicating levels and removing all foliage, nothing has worked. There is seemingly no fix as of now.