Instructions for configuring the Mac to solve this are here:
http://www.robgalbraith.com/diginews..._d1_jpegs.html
Note that this will only help with future D30 images downloaded. The ones already on your drive will not be automatically changed so that they're associated with Photoshop. That can be done easily enough with a program like FileTyper, or about 1 million other shareware apps. You need to change (or rather keep) the file type as JPEG, but change the creator to 8BIM and FileTyper will allow you to do that. You can create a drag and drop droplet that can do folders at a time too.
http://www.ugcs.caltech.edu/~dazuma/filetyper/
Rob Galbraith