This happens when your image is missing the viewBox attribute on the svg element.
Yours should be set to: 0 0 640 480. The zeros are X and Y offsets and the 640 and 480 correspond to the width and height. It defines a rectangle that represents the boundaries of the image.
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" height="480" width="640" viewBox="0 0 640 480">