Crop preview doesn't doesn't resize using W x H Resolution

I'm trying to crop images at specific sizes, but I can't get the W x H x Resolution option to behave like it did in the past.

Step 1:  I select the crop tool and the crop window appears on the image. W x H x Resolution is already selected. All fields are blank.     

Step 2:  I enter the dimensions for W x H x Resolution.  I include 'px' after the dimensions. 

In the past, when entering these dimensions, the crop window would automatically start resizing itself as I typed, and I'd end-up having a new crop window that matched size of the dimensions I just entered.  I could then drag the image around until I like what was being shown in the crop window. 

Now, the crop window does not automatically resize as I type dimensions, it just stays the same size.  Instead, the crop window is now just basically locked to an aspect ratio.  When I resize the crop window, anything I select will be cropped to the dimensions I entered for W x H.  I don't like this behaviour.   

Is it possible I accidentally changed some settings somehow? 

Thanks