If you are printing large images, large numbers of images, or have little memory in the computer; you may wish to alter the memory settings. Indicators that you should do this are:
Memory settings are contained on the Advanced page of the options dialog.
To reduce memory usage, set 'Image Caching' to 'Retrieve image from disk as needed'. This will reduce memory usage considerably, at the expense of making some actions slower.
Reducing the 'Display Image Size' will also reduce memory usage. The only negative of this is that image will appear pixelated (blurrier) on screen. It will not affect how they look when printed.