[Yum] Error in loading repository data

[Loh Chin Huat]

Hi,
I am using Fedora Core release 4 (Stentz) Kernel 2.6.11-1.1369_FC4 on an 
i686. I have previously been using Yum Extender 0.44 - Build : 4, until 
recently I keep encountering the following error. When I launch the 
application, I see in the Output view the following message:

Mirrordetection : best
Cannot open/read repomd.xml file for repository: nrpms
failure: repodata/repomd.xml from nrpms: [Errno 256] No more mirrors to try.

It also display an Error dialogue box stating:

Error in loading repository data
failure: repodata/repomd.xml from nrpms: [Errno 256] No more mirrors to try.

What happened? and what should I do? I have tried to reset repository cache 
but still got the same problem. I wish to update my system to use FC5 and 
also update other applications like OpenOffice. Please assist. Thanks!