2.65a Limit Scale Constraint

I have an armature that consists of two bones and a second armature with only one bone. The bone of the second armature, called “Master” is driving the Y Axis rotation of the second bone of the first armature through its local Y scale.

In order to keep things mathematically legal, I must keep the length of “Master” between 0.728 and 1 Blender Unit. I added a Limit Scale constraint to “Master” with minimum = 0.728 and maximum = 1. I was hoping this would work, but when I scale “Master” in pose mode evrything works until I close in on the minimum value, 0.728. If I drag the mouse beyond this value, lower than 0.728, the first armature snaps back to rest position and my driver “breaks” with an invalid python expression error caused by math.acos taking a value beyond abs(1). I found out it is because the Limit Scale constraint is allowing the mouse position to go lower than the minimum I put in the field, 0.728, even though the bone stops scaling. On a second note the bone, once the mouse crosses the “zero” scale point, flips across the root and proceeds to scale in the negative.

I think I have two problems, first the Limit Scale is reading the mouse position beyond the limit and second, the bone will flip across the root.

How do I keep the Limit Scale from reading beyond my limits and how do I prevent the bone from flipping?

I can give any furthur information upon request.

I do not understand and can’t reproduce the problem. Maybe a picture or a blend.