yum: sometimes it gives me an error

[LilouLinx]

Hello,
I have a problem with using yum. When I install some softwares, 
sometimes yum gives me an error, but some other times it run correctly. 
The error that it gives me is:
    # yum install nvu
    .....
    xcyb-stabl: ################################################## 34/34
    No Match for argument: nvu
    Nothing to do

NB: I'm usin FC3.
Have you a solution for this problem?
Thanks
--------
Lilolinx