Download these config files and replace your old ones with these
http://www.ps3hax.com/index.php?action=tpmod;dl=item46
there is a thread about updating YUM here, shows where the files go:
http://www.ps3hax.com/yellow_dog_lin...mex-t80.0.html
yes, you want to config so that you connect to several update repositories at the same time, make sure you are using the PPC versions of any update sites, which these are. report back.