Lots of errors using speed multiplier in animation (2D).

The character in my 2D platform game uses an animation to crouch, and then another one to crawl when moving while crouched. On the crawl animation I have ticked multiplier in the animator, to multiply the animation speed by the speed of the characters movement. Now when you crawl along at any speed it works, but as soon as you stop, and the speed is 0, the character disappears and then the camera (which is a child of the character at the moment) moves down the scene in big steps. In the console I then get many error messages:-

• Converting invalid MinMaxAABB UnityEditorInternal.InternalEditorUtility:CalculateSelectionBounds(Boolean, Boolean) UnityEditor.DockArea:OnGUI()

• Invalid AABB result UnityEditorInternal.InternalEditorUtility:CalculateSelectionBounds(Boolean, Boolean) UnityEditor.DockArea:OnGUI()

• Quaternion To Matrix conversion failed because input Quaternion is invalid {-1.#IND00, -1.#IND00, -1.#IND00, -1.#IND00} l=-1.#IND00 UnityEditorInternal.InternalEditorUtility:CalculateSelectionBounds(Boolean, Boolean) UnityEditor.DockArea:OnGUI()

• Invalid AABB aabb UnityEditorInternal.InternalEditorUtility:CalculateSelectionBounds(Boolean, Boolean) UnityEditor.DockArea:OnGUI()

• Invalid AABB a UnityEditor.DockArea:OnGUI()

• IsFinite(outDistanceForSort) UnityEditor.DockArea:OnGUI()

• IsFinite(outDistanceAlongView) UnityEditor.DockArea:OnGUI()

These messages loop over and over until I stop the game. I am not using anything to do with OnGUI at the moment. In the animator it is set to go back to the crouch animation when the speed is <0.1. If I untick the multiplier box this doesn't happen, but obviously doesn't look right when crawling slowly.

The weird thing is this used to work fine when I first set it up. It seems to be after I updated my PC to windows 10 (clean install), and reinstalled Unity (5.1.2f1 (64-bit)), although that may be a red herring.

Any ideas???