QLineEdit causes a system beep when it has the focus and return is pressed

To reproduce:

1) On a Mac, compile Qt 4.6.0 (release version) with flags "-no-qt3support -cocoa".
2) Run the examples/widgets/lineedits program
3) Click on one of the line edits to give it the focus (and blinking text caret)
4) Press return
5) Hear the system beep every time return is pressed... annoying!

The system beep is also heard whenever you press up or down arrow key, PageUp, PageDown, Home, End, or a Function Key. Also, if you press Insert, the mouse pointer turns into a question mark, and then if you click on the text in the QLineEdit, it beeps.