[Yum] Not connecting to repositories

[Joelle Tegwen]

I'm not able to connect to the repositories. This just started recently 
and it's happening to me both at home (FC4) and at work (FC5).

I spent a great deal of time at home researching options and trying to 
update repository files all to no avail.
Since it happened to both machines at once I'm wondering if there was a 
conflict that was created in some automatic update (I have the auto up 
dater on for both machines.)

via terminal:
[root at w200356244 ~]# yum list firefox
Loading "installonlyn" plugin
Setting up repositories
livna                                                                [1/6]
flash                                                                [2/6]
jpackage-generic                                                     [3/6]
core                                                                 [4/6]
Cannot find a valid baseurl for repo: core
Error: Cannot find a valid baseurl for repo: core
[root at w200356244 ~]#

via extender:
Mirrordetection : default
Yum Version : 2.6.1 (/usr/share/yum-cli)
Loading "installonlyn" plugin
Cannot find a valid baseurl for repo: core
Cannot find a valid baseurl for repo: extras
Cannot find a valid baseurl for repo: updates
Using default mirror detection
Using default mirror detection
Using default mirror detection
Cannot find a valid baseurl for repo: core

How can I get connected to the repositories?
Thanks in advance for any assistance.
Joelle