Win 7 64 bit
ATI Radeon HD 6850
"Image Crop" does stretch the image if "Image Offset" is unchecked.
Go to Video Sequence Editor and add an Image Strip to it.
In the Panel on the right side check the checkbox "Image Crop" and do some changes to the crop values.
On my PC the Image Preview starts to stretch then, rather then to be cropped.
Only if the above "Image Offset" checkbox also is checked, "Image Crop" works in the expected manner.