A new features called Expose was introduced in Mac OS X 10.3. By default Expose takes control of the F10 key. You'll need to change the hot key for either Expose or F10 Launch Studio so that they're not both using the same key. The hot key for F10 Launch Studio can be change by opening the "System Preferences" and clicking on the F10 Launch Studio icon. Then click the Activation tab. Here you can change the hot key.