I am now using cs5, after years working cs3.
In cs3 I would place an image and could drag the size of the box to fit my document size, however in cs5 the box stays in proportion.
ie draw a blank box and adjust the x and y axis when drawing, now try doing it when placing. I must be missing something and hopefully I have explained it so it is understandable.
Changed behavior. Most users like that.
You can continue to get something similar to the CS3 behavior by either drawing the frame first and palcing the image into it, or by clicking and releasing the mouse to place the image at 100%, then crop and scale.