Comment 1 for bug 283679

I can confirm that this is an annoying bug and is still present in the final release of Intrepid. For some reason, the command to launch WiFi Radar has been changed to use su-to-root instead of gksu. As su-to-root is not part of the default installation or the WiFi radar dependencies - the menu command will normally fail.

http://ubuntuforums.org/showthread.php?t=968741

describes a workaround - but is no excuse for not fixing the bug,