I have installed Red Hat Fedora Core 5. After installation, I tried to add more packages using add/remove packes but the packages manager gave an error the "List of packages cannot be obtained". I have even logged on as root user but it didnot work.
The reason this happens is yum tries to access the net repos everytime to give out a list. Say if a server of one of the repos is handling high load or if your isp has problems, then yum fails.
However thers a sweet little turnaround for this.
Install Kyum from the one of the repos and use Kyum to add/remove packages. Kyum gives you on the fly option to add/remove(enable/disable) repos, besides it doesn't automatically try connecting to the repos. Since Kyum is just a front-end for yum, it modifies the yum config file.
So next time you use yum (add/remove software) and u get the error, simply launch Kyum and disable the repos which might be the problem.
TIP : Better use Kyum for adding/removing packages. Its a gem