Sometimes you may find that the crop tool won't let you define the area you want or it resamples your image after using it. This happens if you have numbers in the height, width, or resolution fields of the options bar (below the menu bar).

After selecting the crop tool, but before dragging out a crop rectangle, click the clear button on the options bar and the tool will behave normally again.

Danny O'Byrne  http://www.digitalartzone.co.uk/

"All the technique in the world doesn't compensate for the inability to notice" Eliott Erwitt