Unable to change dimensions of certain pictures in Word

[jmt356]

I am using MS Word Professional Plus 2010. In my documents, I often have pictures / images copied in. For about half of the them, when I select them I try to change the width or height, nothing happens. I have to manually drag the image to the desired dimensions. I can change the other approximately half of the images by changing the dimensions in the Height and Width boxes. Why can't I modify them for the remaining images?

[HansV]

Could you attach a sample document with one image that can be resized in the dialog, and one that can't? Thanks in advance.