disabling desktop switching shortcut

[debian]

Hi all,

when i go to play supertux, i end up having to press "Ctrl" + "Alt" +
"arrow key" on some parts of the map

the problem is, when i do that, i end up switching between desktops and
killing my game (not the program, but it sure does a number to my score)

How do i disable this shortcut key combo? i tried looking in the
System->preferences->keyboard shortcuts, but i couldnt find anything
that had that key combo

--cj