I don't get it... how come enter will select a highlighted button, but not a highlighted list item? I use a griffen power mate as follows:

Turn Right = Down
Turn Left = Up
Hold+Right = Tab
Hold+Left = Shift-Tab
Press = Enter

When I am on the main menu I can turn left and right to move through the items and select an item by pressing the knob. When I am scrolling though my music list, pressing the knob does nothing. How do I fix this?