Free-look camera y-rotation shake

I created a simple free-look camera by setting the minimum and maximum x/y to -inf and inf and I’ve run into a bug.

http://www.youtube.com/watch?v=HIPhVmeDynU

When the camera crosses its relative axis, the camera y rotation starts to freak out, jumping up to 180 degrees and then back to its original position approximately 30 times per second. I’ve added a quick hack that prevents camera movement outside a certain range to the script, but this feels like I shouldn’t have to do this.

It’s the mouselook with inf and -inf plugged into the limits. There’s no code to see other than the default behaviour when the range of motion is changed in Unity.

[AddComponentMenu("Camera-Control/Mouse Look")]
public class MouseLook : MonoBehaviour {

	public enum RotationAxes { MouseXAndY = 0, MouseX = 1, MouseY = 2 }
	public RotationAxes axes = RotationAxes.MouseXAndY;
	public float sensitivityX = 15F;
	public float sensitivityY = 15F;

	public float minimumX = -360F;
	public float maximumX = 360F;

	public float minimumY = -60F;
	public float maximumY = 60F;

	float rotationY = 0F;

	void Update ()
	{
		if (axes == RotationAxes.MouseXAndY)
		{
			float rotationX = transform.localEulerAngles.y + Input.GetAxis("Mouse X") * sensitivityX;
			
			rotationY += Input.GetAxis("Mouse Y") * sensitivityY;
			rotationY = Mathf.Clamp (rotationY, minimumY, maximumY);
			
			transform.localEulerAngles = new Vector3(-rotationY, rotationX, 0);
		}
		else if (axes == RotationAxes.MouseX)
		{
			transform.Rotate(0, Input.GetAxis("Mouse X") * sensitivityX, 0);
		}
		else
		{
			rotationY += Input.GetAxis("Mouse Y") * sensitivityY;
			rotationY = Mathf.Clamp (rotationY, minimumY, maximumY);
			
			transform.localEulerAngles = new Vector3(-rotationY, transform.localEulerAngles.y, 0);
		}
	}
	
	void Start ()
	{
		// Make the rigid body not change rotation
		if (rigidbody)
			rigidbody.freezeRotation = true;
	}
}

Here stills shaking!