There is a file save bug that does that sometimes. Even little scenes (under 50MB) can hit the 2GB bug. The 2GB file is corrupt and cannot be opened or used in any way. Luckily it can be deleted.
I have never seen either the cause or the solution to the problem.

EDIT - I have never had the bug myself; but have seen posts about it.

Friends don't let friends use booleans.