I’m a complete Photoshop novice, often getting FranX or Lee to walk me through stuff. One observation I thought I would share about Photoshop 7 running in OS X: when working on a JPG (and maybe any file), be sure to not have that file selected in the Finder.
I had clicked on the JPG in question in the Finder (column view), and the Finder was previewing the pic. Photoshop no likee this. As soon as I clicked to another pic in the Finder, Photoshop saved my changes to the JPG.