Digital Light & Color

Making a Margins or Borders change with a 1:1 Small Preview will also initiate a Preview "Zoom to 1:1 and Resize".

File/Preference settings:
Default Preview: Auto
Preview Size: Small -- Upper Right

1) open an image into the work space...
2) open the Crop,Add Border transform with Auto Preview checked...
3) change Preview to "Zoom to 1:1"... ...Preview size remains Small...
4) make a Margins or Borders change... ...Preview updates as expected but also will Resize to the available workspace area covering any other open dialogs and images.

...den...
Vista 32 Home Premium, SP2, latest version/updates
AMD Athlon 64 x2 6000+ processor
3 GB DDR2 dual channel RAM
2 MB ReadyBoost Cache
500GB hard drive with 100GB free space

This was a deliberate change in the latest version - it causes the preview to be reset whenever the preview image changes size. Previously the preview window would either be cut off and have scroll bars or it would have a large border.

I prefer the latest version (preview window adapts to the cropped image) over the previous one.