Thank you for your response.
I'm using https://github.com/codeinvain/Box2DFlex
, which I believe slightly modifies the core Box2D for Flex. No forum for it, but I can check with the owner.
I'm very sure the leak is with B2Vec2 Box2D Common.Math, because that is the only object where the memory in growing in the Profiler. See attached screen shot. The leak grows very fast. gets to about 500MB in about 10 min. It keeps growing until it maxes out the PC memory.
I have seen a lot of posts in google about B2Vec2 memory leaks with folks using various versions.
I may have to look into getting away from the Flex version and try the latest pure AS3 version.