Hi Mad,
We've found a solution for this problem: You just need to delete all objects from the scene used in the Instanced geometry!
As a result, all references between GrowFX objects will be broken, and recalculation all of GrowFX objects that have the Instantced geometry, will not occur when you rescaling an object.
However, GrowFX will keep these objects, and if necessary you can extract them...
Thanks!