OS 10.4 - default app change not sticking

I'm trying to change the default application that opens up my jpg files, but the change isn't sticking.

Here's what's happening:
I highlight a jpg file, and press command-i to bring up the info window. In the "open with" box, the current selection is Preview. I click the arrows next to open with, and list drops down with 13 apps listed. None is the one I want, so I click "other".

Now I have a window labeled "choose another application". There's a box at top that reads Enable:Recommended Apllication. I navigate to the application I want (Photo Studio), and select it. (On this window there's also a checkbox labled "Always open with" - I've tried checking it and leaving it unchecked.) I click Add.

Now I'm back at the info window. It now reads open withhoto Studio. I click "change all". A message box pops up that reads:
"Are you sure you want to change all your photo studio documents to open with the application "PhotoStudio""

I click continue and I'm back at the info window which has reverted to open withreview.

If I choose one of the 13 applications in the open with drop down list and go through the same steps, it doesn't revert to Preview.

How do I make Photo Studio the default app for my jpgs?