The problems I have seen with Photoshop on Leopard and Snow Leopard generally fall into one of several categories:
- Font problems. Photoshop will often choke, crash, freeze, bring up the spinning beachball, or otherwise malfunction if you have a corrupt font on the system, it is quite likely that this is the source of your trouble. Disable all non-system fonts and see if that helps.
- Adobe Bridge problems. I've had a lot of trouble with Bridge on Leopard and Snow leopard. Remove it with your installer and see if that helps.
- A bad plugin, most *especially* a bad scanner or multifunction printer/scanner plugin. These may be located in the Photoshop plugins folder (usually in Import/Export), or in your TWAIN Data Sources folder which is in your Image Capture folder inside your Library folder on your hard drive. Remove any plugins in Import/Export in the Photoshop plugins folder or in your TWAIn folder and see what happens.
Those are the first places I'd look. If oyu still keep having problems, post back and we can try another round of troubleshooting!