My way of playing music off usb:
Go to the usb drive in the music section. Don't open it yet. Press triangle on it. Then there's an option that lets you browse through the directory structure (Can't remember), select that.
Copy files to ps3. Listen.
15/08/2007
I'm currently located in a place, which, according to my presence, may or may not contain traces of Kiah. This may be subject to changes within the next few months. See your pharmacist for more detail