Hi,

The first thing I thought of is that if you select the photo, e.g. by clicking in the margin to the left of the photo (the cursor being the white arrow pointing diagonally to the top right) then the photo goes into negative colours. If you click anywhere in the document (not in the margin) after that the picture will de-select and go back to the correct colours.

Sorry, a simplistic explanation, but it makes sense that it would make the photo negative but not affect the printed output.

Helen