the command is ethereal, not Ethereal.
packages, normal users can only run ethereal so that it captures packets on the loopback interface (I believe)... maybe on FC they cannot run it at all (which seems logical to me : such tools may be really harmfull in bad hands).
Didn't you try to 'locate' ethereal, so that you can check wether the program is on root's path ?
I don't think that this is a FC issue... ethereal is used by lots of people and such a problem would have been noticed and fixed.
Last remark : ethereal is run through a front end, so you need to 'xhost +' as the user that owns the X session and then "export DISPLAY=:0.0" as root, so that root can run graphical programs.