On your failing machine, if you have clearos-centos-verified enabled you should also enable clearos-centos-updates-verified.

If you wanted to find the answer to what made it work, have a look you your yum log and check out the packages which were installed at the time with the yumdb command, or perhaps with "yum --enablerepo=* list --showduplicates then_your_package_list" which marks each package which you have installed.