You are experiencing mirror problems. These problems have been reduced in the newer version of smeserver-yum with the mirrorlist and fastestmirror options. These options try to find the closest/fastest mirror and if that mirror fails it will try another.
"7.0c3" I presume you mean 7.0rc3 and if that's the case, there are MANY updates since then and this is most likely why you are having some problems.
You may want to try just updating yum first and then try a full update after.
WARNING: The version of smeserver-yum that is in smeupdates-testing may break the yum server manager panel. It is currently being worked on so you will have to do everything from the command line. This version employs the fastestmirror and mirrorlist options and works much better.
yum clean all
yum --enablerepo=smeupdates-testing update *yum*
signal-event post-upgrade
signal-event reboot