Quicktime Picture Viewer

The "Change All" button works on the file extension (in this case .jpg or even .jpeg) and not the file "creator" (the open with app). It is all or nothing.
You can always just right-click (Control-click) and pick the app you want to use from the pull down menu. You can also drag the file icon to any app icon and, if it can open the file, it will highlight. Drop the icon on the app icon to open.

Try this. If all the files that you want to change are in one folder, highlight them all - Command (Apple key)/A keys - when they are all highlighted, right mouse click to bring the Get Info panel up. Press the Alt key - you will see that Get Info changes to Show Inspector - keeping the Alt key pressed, click that. In the panel that pops up, choose the app you want in the Open With button. You should notice that as soon as you pick another app all the icons that you have highlighted will change to that app. WITHOUT clicking the Change All button, close the panel (red button top left corner). All the icons (and only those icons) that you first highlighted should now open with the app you chose.

When you first have all your icons highlighted together, DO NOT click the Get Info button. If you do they'll all open their own Info Panel - won't do any harm, it's just a pain to have to go round closing them all separately.

iMac G5 20in 1.8 Ghz Mac OS X (10.4.6) 2 GB RAM