Photoshop Elements :: How To Save Files With A Lower Case Extension By Default

I'm using PSE 9 on a new Mac Mini. I want to be able to save files with a lower-case extension by default. With my main (non-administrator) account, the extension is there, but it's always in uppercase. I've tried to select the "Use lower-case" option, but it always comes in upper-case, and when I go back to the preferences, the "Use lower-case" option is unselected. In my administrator account, I can't even get the "Always use an extension" option to stay selected.