Snow Leopard does something funny with disk images: it always defaults to showing their contents in Icons view, no matter what Finder view you prefer. A group of Mac OS X Hints readers discovered a workaround to fix this problem:
Let’s say you create a new disk image on your desktop (encrypted or not, with read and write privileges) and put some files in it. If you mount that image and double-click on it on the desktop, those files will appear in Icons view. (If you open it from the Finder sidebar, it’ll open in whatever view you’re currently using.) You can select another view from the View menu (List, Columns, or Cover Flow). But if you close then reopen the window, the view will revert to Icons. This appears to happen in all versions of Snow Leopard through 10.6.4.
Here’s the workaround: mount the Disk Image and double-click on its icon on the desktop. It will open in Icons view. Press Command-J to display the view options box. Check the Always Open in Icon View box. (Yes, you read that right).
Now, with the view options box still visible, switch to another view using either the View menu or a keyboard shortcut (Command-2 for List, Command-3 for Columns, or Command-4 for Cover Flow). Uncheck the Always Open in Icon View box – it should change to reflect the current view – and then reselect it. If you then close and reopen the disk image’s Finder window, you should see the files in your preferred view. Unfortunately, this setting will stay in effect only as long as that disk image is mounted; once you unmount it, the setting will go back to Icons view and you’ll have to repeat this process.