It seems to work for me, let's examine what you're doing compared to what I'm doing to see where we differ.
1) Create three shapes on top of each other.
2) Select all three shapes.
3) Arrange > Distribute Objects > Horizontally
What should happen is that the objects should spread out horizontally such that the bounding box on the right of one touches the bounding box on the left of the other. Something similar should happen when you distribute Vertically.
If shapes work right, then the difference must be between images and shapes. Click your image, check the "Wrap" tab in the inspector and see what Object Placement is set to be. If it's Inline, then there's more than just the image's position determining where it will go.