Press Step over Hot key "F10" when debugging, qt creator have no action on Linux Ubuntu 11.10

Steps:
1. Open a qt gui example application e.g. animatedtiles.
2. Setup some break points in main function in main.cpp file.
3. Set the target to desktop debugging.( 4.7.4 or 4.8 debug ).
4. Start debugging.
5. Check the debug menu, to see if the hotkey of "Step Over" is "F10".
5. Try to Press "F10" key to test if the process step over.

Expected Result:
step over in code after press "F10"
Actually Result:
Nothing done by qt creator after press "F10" key.

Only occurs when I use Ubuntu( or Ubuntu 2D) UI.